Global cooling: cold acclimation and the expression of soluble proteins in carp skeletal muscle

The common carp (Cyprinus carpio) has a well-developed capacity to modify muscle properties in response to changes in temperature. Understanding the mechanisms underpinning this phenotypic response at the protein level may provide fundamental insights into the molecular basis of adaptive processes in skeletal muscle. In this study, common carp were subjected to a cooling regimen and soluble extracts of muscle homogenates were separated by 1-D SDS-PAGE and 2-DE. Proteins were identified using MALDI-TOF-MS and de novo peptide sequencing using LC-MS/MS. The 2-D gel was populated with numerous protein spots that were fragments of all three muscle isoforms (M1, M2 and M3) of carp creatine kinase (CK). The accumulation of the CK fragments was enhanced when the carp were cooled to 10 degrees C. The protein changes observed in the skeletal muscle of carp subjected to cold acclimation were compared to changes described in a previous transcript analysis study. Genes encoding CK isoforms were downregulated and the genes encoding key proteins of the ubiquitin-proteasome pathway were upregulated. These findings are consistent with a specific cold-induced enhancement of proteolysis of CK.

The supramolecular assemblies of voltage-dependent anion channels in the native membrane

Voltage-dependent anion channels (VDACs) are major constituents of the outer mitochondrial membrane (OMM). These primary transporters of nucleotides, ions and metabolites mediate a substantial portion of the OMM molecular traffic. To study the native supramolecular organization of the VDAC, we have isolated, characterized and imaged OMMs from potato tubers. SDS-PAGE and mass spectrometry of OMMs revealed the presence of the VDAC isoforms POM34 and POM36, as well as the translocase of the OMM complex. Tubular two-dimensional crystals of the VDAC spontaneously formed after incubation of OMMs for two to three months at 4 degrees C. Transmission electron microscopy revealed an oblique lattice and unit cells housing six circular depressions arranged in a hexagon. Atomic force microscopy of freshly isolated OMMs demonstrated (i) the existence of monomers to tetramers, hexamers and higher oligomers of the VDAC and (ii) its spatial arrangement within the oligomers in the native membrane. We discuss the importance of the observed oligomerization for modulation of the VDAC function, for the binding of hexokinase and creatine kinase to the OMM and for mitochondria-mediated apoptosis.

Purification and some properties of two creatine kinase isoforms from herring (Clupea harengus) spermatozoa

Creatine kinase (CK, EC 2.7.3.2) isoforms play important role in energy homeostasis and together with easily diffusible compounds like creatine and phosphocreatine maintain a cellular energy buffer and intracellular energy transport system. The CK activity in spermatozoa is the highest from all studied tissues in herring. It was detected that the two CK isoforms, CK1 and CK2, are characteristic only for spermatozoa and are not expressed in other herring tissues. Isolation and purification procedures allowed obtaining purified enzymes with specific activity of the 345 micromol/min/mg for CK1 and 511 micromol/min/mg for CK2. Native Mr's of the CK1 and CK2 determined by gel permeation chromatography were about 330,000 and 90,000, respectively. These results indicate that CK1 form has octameric structure and CK2 is a dimer mostly characteristic for cytosolic CK enzymes. In immunoblotting studies with antisera against CK2, the response was observed for CK2 and there was no response for CK1 and two other isoforms from herring skeletal muscle. These findings make the herring isoforms an interesting model for studies on the fish CK biochemical properties.

Analysis of cardiolipin in human muscle biopsy

Cardiolipin is a phospholipid that is specific to the inner mitochondrial membrane and essential for numerous mitochondrial functions. Accordingly, a quantitative assay for cardiolipin can be a valuable aspect of assessing mitochondrial content and functional capacity. The current study was undertaken to develop a simple and reliable method for direct analysis of the major molecular species of cardiolipin and with particular application for analysis of human skeletal muscle. The method that is presented is based on derivatization of cardiolipin in a total lipid extract with 1-pyrenyldiazomethane (PDAM), to form stable, fluorescent 1-pyrenylmethyl esters. The derivatization reaction takes 30 min on ice in a two-phase system (chloroform:methanol:H(2)O:H(2)SO(4)) containing 0.5-1.0mM PDAM and detergent. The contents of the major cardiolipin species in the derivatization mixture can be estimated by HPLC separation with fluorescent detection during a 20 min run on a reverse phase column and with HPLC grade ethanol/0.5mM H(3)PO(4) as the mobile phase. The recovery is about 80%. The method is specific and sensitive with quantitation limits of 0.5-1 pmol cardiolipin. The response of the fluorescence detector (peak area) is linear across a range 5-40 pmol. The assay is linear over the range between 0.3 and 3.0mg of tissue (R(2)=0.998). The assay provides good reproducibility and accuracy (within 5-10%).

Characterization of creatine kinase isoforms in herring (Clupea harengus) skeletal muscle

It is known that mitochondrial creatine kinase (MtCK) in mammals is always expressed in conjunction with one of the cytosolic forms of creatine kinase (CK), either muscle-type (MM-CK) or brain-type (BB-CK) in tissues of high, sudden energy demand. The two creatine kinase (CK) isoforms were detected in herring (Clupea harengus) skeletal muscle: cytosolic CK and mitochondrial CK (MtCK) that displayed the different electrophoretic mobility. These isoforms differ in molecular weight and some biochemical properties. Isolation and purification procedures allowed to obtain purified enzymes with specific activity of the 206 micromol/min/mg for cytosolic CK and 240 micromol/min/mg for MtCK. Native M(r)s of the cytosolic CK and MtCK determined by gel permeation chromatography were 86.000 and 345.000, respectively. The results indicate that one of isoforms found in herring skeletal muscle is a cytosolic dimer and the other one, is a mitochondrial octamer. Octamerization of MtCK is not an advanced feature and also exists in fish. These values correspond well with published values for MtCKs and cytosolic CK isoforms from higher vertebrate classes and even from lower invertebrates.

Relating structure to mechanism in creatine kinase

Found in all vertebrates, creatine kinase catalyzes the reversible reaction of creatine and ATP forming phosphocreatine and ADP. Phosphocreatine may be viewed as a reservoir of "high-energy phosphate" which is able to supply ATP, the primary energy source in bioenergetics, on demand. Consequently, creatine kinase plays a significant role in energy homeostasis of cells with intermittently high energy requirements. The enzyme is of clinical importance and its levels are routinely used as an indicator of myocardial and skeletal muscle disorders and for the diagnosis of acute myocardial infarction. First identified in 1928, the enzyme has undergone intensive investigation for over 75 years. There are four major isozymes, two cytosolic and two mitochondrial, which form dimers and octamers, respectively. Depending on the pH, the enzyme operates by a random or an ordered bimolecular mechanism, with the equilibrium lying towards phosphocreatine production. Evidence suggests that conversion of creatine to phosphocreatine occurs via the in-line transfer of a phosphoryl group from ATP. A recent X-ray structure of creatine kinase bound to a transition state analog complex confirmed many of the predictions based on kinetic, spectroscopic, and mutagenesis studies. This review summarizes and correlates the more significant mechanistic and structural studies on creatine kinase.

Isolation, characterization, and cDNA-derived amino acid sequence of glycocyamine kinase from the tropical marine worm Namalycastis sp

We isolated cytoplasmic glycocyamine kinase (GK) and creatine kinase (CK) from the tropical marine worm Namalycastis sp. by ammonium sulfate fractionation, gel filtration on Sephacryl S-200, and DEAE-5PW chromatography. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) showed that the isolated GK is highly purified and appears to be a heterodimer of two distinct subunits, alpha and beta, with molecular masses of approximately 40 kDa. The complete nucleotide sequences of the cDNAs for Namalycastis GKalpha and GKbeta were 1527 (encoding 374 amino acids) and 1579 bp (encoding 390 amino acids), respectively. The predicted amino acid sequences differ only in the N-terminal 50 residues. This is consistent with the characteristics of Neanthes GKalpha and GKbeta chains, which we have previously shown to be generated by alternative splicing. The recombinant enzymes GKalpha, GKbeta, and CK from Namalycastis were successfully expressed in Escherichia coli as maltose-binding protein fusion proteins. In contrast to the stable GKbeta enzyme, GKalpha was quite unstable, and its activity decreased remarkably with time. Thus, the N-terminal 50 residues appear to play a key role in enzyme stability. The kinetic parameters for the native GK heterodimer were similar to GKbeta, suggesting that GKalpha would have an activity similar to GKbeta if part of a heterodimer. This is the first report of precise kinetic parameters for GK. Finally, based on our results, we present a model for pluriphosphagen function in Namalycastis wherein cytoplasmic GK and CK and mitochondrial CK function together with phosphocreatine and phosphoglycocyamine to enable cells to respond quickly to a sudden large energy requirement.

Immunoaffinity purification of SRT-tagged human creatine kinase by peptide elution

The mouse monoclonal antibody (Mab), SRT10, recognizes a linear epitope of 10 amino acids (ThrPheIleGlyAlaIleAlaThrAspThr). When these epitope-tagged fusion proteins are expressed in mammalian cells, the Mab can detect the tagged proteins by immunoblotting, immunocytochemistry and immunoprecipitation. Here, we describe an efficient method for the purification of SRT-tagged recombinant human creatine kinase (CK) transiently expressed in mammalian cells. This method utilizes the expression of the N-terminal- or C-terminal-tagged CK in transiently transfected HEK293 cells followed by binding to anti-SRT-agarose affinity resin and competitive elution with SRT peptide. Recombinant CK was purified near homogeneity as judged by SDS-PAGE.

Isolation, characterization and nucleotide sequence of the muscle isoforms of creatine kinase from the Antarctic teleost Chaenocephalus aceratus

Creatine kinase (CK) was isolated from the white muscle of the Antarctic icefish Chaenocephalus aceratus, which is deficient in glycolytic capacity. C. aceratus white myotomal creatine kinase (MMCK) displayed an apparent K(m) at 0.5 degrees C of 0.06 mM for ADP and 17 mM for Phosphocreatine. These K(m) values are similar to those reported for other vertebrate MMCKs at their physiologically relevant body temperatures. C. aceratus MMCK exhibited optimal activity at pH of 7.6-7.7 at 0.5 degrees C, in contrast to rabbit MMCK which had optimum activity at pH 6.2 at 30 degrees C. The apparent V(max) of C. aceratus MMCK at 0.5 degrees C is 94+/-4 S.D. (n=9) micromol ATP/min/mg (i.e. U/mg), which is comparable to rabbit MMCK assayed at 20 degrees C and 8-fold greater than rabbit MMCK measured at 0.5 degrees C. DEAE chromatography of C. aceratus white muscle CK resolved two distinct activity peaks. Cloning and sequencing of C. aceratus CK cDNAs confirmed that two muscle-specific isoforms of CK were expressed that were distinct from the mitochondrial and brain isoforms. Icefish MMCK was sensitive to transient temperature elevation, and the DEAE-fractionated forms were highly unstable. These results indicate that C. aceratus MMCK displays significant activity at physiological temperature and intracellular pH of icefish muscle that could contribute to sustaining energy charge during burst-swimming.

[ATP-generating creatine kinase: a new compound isolated from Viperidae venom]

This is a first report on the presence of creatine kinase, ATP-generating enzyme, in the venom of Vipera xanthia representing the Viperidae family of poisoning snakes. Kinetic and catalytic properties of 40 kD active monomer has been described with a following discussion on the issue of potential of the data listed for further research in either toxic coagulopathy molecular mode or enzyme application dealing with "thrombin-thrombin receptor" interaction studies. An enzyme purification procedure includes hydrophobic (phenyl-Sepharose), anion exchange (MonoQ) and affinity (ADP-Sepharose) chromatographic steps.

Measuring synthesis rates of muscle creatine kinase and myosin with stable isotopes and mass spectrometry

We investigated a novel strategy for measuring the synthesis rate of proteins in skeletal and cardiac muscle. Mass isotopomer distribution analysis allows measurement of the isotopic enrichment of the true biosynthetic precursor for proteins (tRNA-amino acids), but cannot easily be applied to slow turnover muscle proteins due to insufficient isotope incorporation into multiply labeled species. Using a rapid turnover protein from the same tissue, however, might reveal tRNA-amino acid enrichment. We tested this strategy in rats on muscle creatine kinase (CK). A trypsinization peptide (3647u) containing 5 leucine repeats was identified by computer-simulated digestion of CK and then isolated from trypsin hydrolysates. Mass isotopomer abundances were determined by electrospray ionization-magnetic sector-mass spectrometry after in vivo administration of [(2)H(3)]leucine. Myosin heavy chain was also isolated and hydrolyzed to free amino acids. Muscle tRNA-amino acids were well labeled, by direct measurement. Enrichments of M(+1) and M(+2) mass isotopomers in the CK-peptide were measurable but low (consistent with a CK half-life of 3-10 days). Incorporation into skeletal muscle myosin indicated a half-life of 54 days. In conclusion, the general strategy of measuring protein kinetics by quantifying mass isotopomer abundances of mid-sized peptides from protein hydrolysates is effective, but CK does not turn over rapidly in muscle, contrary to previous reports. Identification of a rapid turnover muscle protein would be useful for this purpose.

Expression of Torpedo californica creatine kinase in Escherichia coli and purification from inclusion bodies

The pET17 expression vector was used to express creatine kinase from the electric organ of Torpedo californica as inclusion bodies in Escherichia coli BL21(DE3) cells. The insoluble aggregate was dissolved in 8M urea and, following extraction with Triton X-100, the enzyme was refolded by dialysis against Tris buffer (pH 8.0) containing 0.2M NaCl. After two buffer changes, chromatography on Blue Sepharose was used as a final step in the purification procedure. Approximately 54mg active protein was recovered from a 1L culture and the refolded enzyme had a specific activity of 75U/mg. The molecular mass of the purified protein was consistent with that predicted from the amino acid sequence and the CD spectrum of the refolded enzyme was essentially identical to that of creatine kinase from human muscle (HMCK). The K(m) values of ATP and ADP were also similar to those of HMCK, while the K(m) values for both phosphocreatine and creatine were approximately 5-10-fold higher. The purification described here is in marked contrast with earlier attempts at purification of this isozyme where, in a process yielding less than 1mg/L culture, enzyme with a specific activity of ca. 5U/mg was obtained.

Isolation and characterization of the muscle-specific isoform of creatine kinase from the zebrafish, Danio rerio

We have isolated and characterized a cDNA sequence corresponding to the zebrafish muscle-specific isoform of creatine kinase. The sequence is 1552 bases in length and contains an open reading frame capable of producing a 381 amino acid protein. The sequence is very similar to muscle-specific creatine kinases isolated from other species at both the nucleotide and amino acid levels but contains some differences from a previously reported zebrafish clone.

Lead ion effect on creatine kinase: equilibrium and kinetic studies of inactivation and conformational changes

The effects of lead ions on creatine kinase (CK) were studied by measuring activity changes, intrinsic fluorescence spectra and 8-anilo-1-naphthalenesulfonate (ANS)-binding fluorescence along with size-exclusion chromatography (SEC). Below 5 mM Pb(2+) concentration, there was nearly no change of the enzyme activity and a slight change of the ANS-binding fluorescence. The CK activity decreased significantly from 10 to 25 mM Pb(2+) concentrations. No residual activity was observed above 25 mM Pb(2+). The kinetic time courses of inactivity and unfolding were all mono-phase courses with the inactivation rate constants being greater than the unfolding rate constants for the same Pb(2+) concentration. The changes in fluorescence maximum and fluorescence intensity were relatively slow for 40-80 mM Pb(2+) as well as in the initial stage for less than 5 mM Pb(2+), showing that two transition states exist for Pb(2+) induced equilibrium-unfolding curves. The intrinsic fluorescence spectra and ANS-binding fluorescence measurements showed that even for high Pb(2+) concentrations, CK did not fully unfold. Additionally, the SEC results showed that the enzyme molecule still existed in an inactive dimeric state at 20 and 40 mM Pb(2+) solutions. All the results indicated the presence of at least one stable unfolding equilibrium intermediate of CK during Pb(2+) unfolding.

Effect of osmolytes as folding aids on creatine kinase refolding pathway

The influence of osmolytes, including dimethysulfoxide, glycine, proline and sucrose, on the refolding and reactivation courses of guanidine-denatured creatine kinase was studied by fluorescence emission spectra, circular dichroism spectra, recovery of enzymatic activity and aggregation. The results showed that low concentrations of dimethysulfoxide (<20%), glycine (<0.5 M), proline (<1 M) and sucrose (<0.75 M) improved the refolding yields of creatine kinase, but high osmolyte concentrations decreased its recovery. Sucrose favored the secondary structural formation of creatine kinase. Proline and sucrose facilitated refolding of the protein to its original conformation, while dimethysulfoxide and proline accelerated the hydrophobic collapse of creatine kinase to a packed protein. During the aggregation of creatine kinase, dimethysulfoxide and sucrose inhibited aggregation of creatine kinase, as did proline, but glycine was unable to inhibit aggregation. These systematic observations further support the suggestion that osmolytes, including low concentrations of dimethysulfoxide, proline or sucrose, possibly play a chaperone role in the refolding of creatine kinase. The results also indicate that sucrose and free amino acids are not only energy substrates and organic components in vivo, but also help correct protein folding.

An unusually low pK(a) for Cys282 in the active site of human muscle creatine kinase

All phosphagen kinases contain a conserved cysteine residue which has been shown by crystallographic studies, on both creatine kinase and arginine kinase, to be located in the active site. There are conflicting reports as to whether this cysteine is essential for catalysis. In this study we have used site-directed mutagenesis to replace Cys282 of human muscle creatine kinase with serine and methionine. In addition, we have replaced Cys282, conserved across all creatine kinases, with alanine. No activity was found with the C282M mutant. The C282S mutant showed significant, albeit greatly reduced, activity in both the forward (creatine phosphorylation) and reverse (MgADP phosphorylation) reactions. The K(m) for creatine was increased approximately 10-fold, but the K(m) for phosphocreatine was relatively unaffected. The V and V/K pH-profiles for the wild-type enzyme were similar to those reported for rabbit muscle creatine kinase, the most widely studied creatine kinase isozyme. However, the V/K(creatine) profile for the C282S mutant was missing a pK of 5.4. This suggests that Cys282 exists as the thiolate anion, and is necessary for the optimal binding of creatine. The low pK of Cys282 was also determined spectrophotometrically and found to be 5.6 +/- 0.1. The S284A mutant was found to have reduced catalytic activity, as well as a 15-fold increase in K(m) for creatine. The pK(a) of Cys282 in this mutant was found to be 6.7 +/- 0.1, indicating that H-bonding to Ser284 is an important, but not the sole, factor contributing to the unusually low pK(a) of Cys282.

Adenine nucleotide translocator isoforms 1 and 2 are differently distributed in the mitochondrial inner membrane and have distinct affinities to cyclophilin D

Different isoforms of the adenine nucleotide translocase (ANT) are expressed in a tissue-specific manner. It was assumed that ANT-1 and ANT-2 co-exist in every single mitochondrion and might be differently distributed within the membrane structures that constitute the peripheral inner membrane or the crista membrane. To discriminate between ANT originating from peripheral or from cristal inner membranes we made use of the fact that complexes between porin, the outer-membrane pore protein, and the ANT can be generated. Such complexes between porin and the ANT in the peripheral inner membrane were induced in rat heart mitochondria and isolated from rat brain and kidney. Using ANT-isotype-specific antibodies and sequence analysis of the N-terminal end, it was discovered that the peripheral inner membrane contained ANT-1 and ANT-2, whereas the cristal membrane contained exclusively ANT-2. Cyclophilin was co-purified with the porin-ANT complexes, whereas it was absent in the crista-derived ANT. This suggested that ANT-1 might have a higher affinity for cyclophilin. This specific intra-mitochondrial distribution of the two ANT isotypes and cyclophilin D suggests specific functions of the peripheral and crista-forming parts of the inner membrane and the two ANT isotypes therein.

Mutagenesis of two acidic active site residues in human muscle creatine kinase: implications for the catalytic mechanism

Creatine kinase (CK) catalyzes the reversible phosphorylation of the guanidine substrate, creatine, by MgATP. Although several X-ray crystal structures of various isoforms of creatine kinase have been published, the detailed catalytic mechanism remains unresolved. A crystal structure of the CK homologue, arginine kinase (AK), complexed with the transition-state analogue (arginine-nitrate-ADP), has revealed two carboxylate amino acid residues (Glu225 and Glu314) within 2.8 A of the proposed transphosphorylation site. These two residues are the putative catalytic groups that may promote nucleophilic attack by the guanidine amino group on the gamma-phosphate of ATP. From primary sequence alignments of arginine kinases and creatine kinases, we have identified two homologous creatine kinase acidic amino acid residues (Glu232 and Asp326), and these were targeted for examination of their potential roles in the CK mechanism. Using site-directed mutagenesis, we have made several substitutions at these two positions. The results indicate that of these two residues the Glu232 is the likely catalytic residue while Asp326 likely performs a role in properly aligning substrates for catalysis.

Production of recombinant human creatine kinase (r-hCK) isozymes by tandem repeat expression of M and B genes and characterization of r-hCK-MB

BACKGROUND

Serum creatine kinase-MB isoenzyme (CK-MB) is widely used as a marker of myocardial injury. We prepared recombinant human CK (r-hCK) MB isoenzyme and examined its potential for use as a control material for assay of CK-MB in serum.

METHODS

cDNAs encoding CK-M and CK-B subunits were inserted into the same plasmid vector, followed by transformation of Escherichia coli. The resulting three types of CK isoenzymes were purified by conventional chromatography.

RESULTS

The ratio of MB to MM to BB was 50:40:10 on the basis of CK activity. Highly purified CK-MB with a specific activity of 533 U/mg was produced in a yield of 5.7 mg/g of packed cells. Purified r-hCK-MB had the isoelectric point (pI 5.3) and molecular size (46 kDa for the subunit) of native CK-MB. Its immunoreactivity in an ELISA using antibody against native heart enzyme was similar to that of cardiac CK-MB. The r-hCK-MB retained >90% activity for at least 4 months at 11 degrees C in a delipidated serum matrix in a liquid form at a concentration of 118 U/L.

CONCLUSIONS

r-hCK-MB shows key properties of the native cardiac isoenzyme and may be useful as a control and calibrator for serum assays of CK-MB.

Divergent enzyme kinetics and structural properties of the two human mitochondrial creatine kinase isoenzymes

The mitochondrial isoenzymes of creatine kinase (MtCK), ubiquitous uMtCK and sarcomeric sMtCK, are key enzymes of oxidative cellular energy metabolism and play an important role in human health and disease. Very little is known about uMtCK in general, or about sMtCK of human origin. Here we have heterologously expressed and purified both human MtCK isoenzymes to perform a biochemical, kinetic and structural characterization. Both isoenzymes occurred as octamers, which can dissociate into dimers. Distinct Stokes' radii of uMtCK and sMtCK in solution were indicative for conformational differences between these equally sized proteins. Both human MtCKs formed 2D-crystals on cardiolipin layers, which revealed further subtle differences in octamer structure and stability. Octameric human sMtCK displayed p4 symmetry with lattice parameters of 145 A, indicating a 'flattening' of the octamer on the phospholipid layer. pH optima and enzyme kinetic constants of the two human isoenzymes were significantly different. A pronounced substrate binding synergism (Kd > Km) was observed for all substrates, but was most pronounced in the forward reaction (PCr production) of uMtCK and led to a significantly lower Km for creatine (1.01 mM) and ATP (0.11 mM) as compared to sMtCK (creatine, 7.31 mM; ATP, 0.68 mM).

A dimeric creatine kinase from a sponge: implications in terms of phosphagen kinase evolution

This study demonstrates conclusively that tissues of the sponge Tethya aurantia contain significant creatine kinase (CK) activity. This CK was purified and analyzed with respect to a number of physico-chemical properties. Size exclusion chromatography and denaturing gel electrophoresis analyses showed that this enzyme is dimeric. The sequences of several Lys-C endoproteinase peptides from Tethya CK are consistent with this enzyme being a member of the phosphagen kinase family and a true CK. CK in higher organisms exists in a variety of quaternary structure forms--dimer, octamer and large monomer consisting of a three contiguous CK domains. The present results indicate that CK evolved very early in metazoan evolution and that the dimeric structure preceded other subunit association forms.

Purification and partial characterization of creatine kinase from electric organ of Electrophorus electricus (L.)

The present investigation deals with the purification and the partial characterization of the soluble creatine kinase (CK) isoenzyme, isolated from the electric organ electrocyte of Electrophorus electricus (L.). Purification was performed by precipitation of the enzyme in the crude extract with ammonium sulfate (80%). The precipitate obtained was analyzed on an ion exchange column of diethylaminoethyl cellulose-52 (DEAE) followed by gel filtration on Superose 12 in a Fast Protein Liquid Chromatography (FPLC) system. Electrophoretic mobility of the active peak confirmed previous results identifying the hybrid isoenzyme MB in the electrocyte cytoplasm. Electrocyte CK is a dimeric enzyme with two identical subunits of approximately 40 kDa as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The sequence analysis of the N-terminal peptide (14 amino acids) of the 40 kDa subunit showed homology with other CK enzymes from electric fish (Torpedo) and human muscle type CK.

A complete system for identifying inhibitors of creatine kinase B

We have developed a complete system for discovery of lead compounds as inhibitors of creatine kinase B. In this article, we describe production and purification of the recombinant protein, conditions and features of an optimized high-throughput screening assay, and results of our implementation of the system using a diverse compound library.

Characterization of two types of mitochondrial creatine kinase isolated from normal human cardiac muscle and brain tissue

Two types of mitochondrial creatine kinase (Mi-CK), sarcomeric (sMi-) and ubiquitous (uMi-)CKs, were isolated from normal human cardiac muscle and brain tissue, respectively, and their heterogeneity was characterized by means of isoelectric focusing (IEF). Octameric sMi-CK and uMi-CK were electrophoresed cathodic to cytoplasmic muscle-type creatine kinase isoenzyme (CK-MM) and dimeric Mi-CKs were found at the position of CK-MM on a cellulose acetate membrane. The electrophoretic mobilities of sMi-CK were similar to those of uMi-CK. Octameric sMi-CK was focused at pI 7.1-8.0 and dimeric forms at pI 6.55, 6.75, 6.85, and 6.95. New bands appearing at pI 6.65 and 6.75 after treatment of sMi-CK with carboxypeptidase B were found to be delysined forms. sMi-CK reacted with anti-sMi-CK antibodies, and the immune complexes were focused at pI 5.8. The Km value of sMi-CK for creatine phosphate (PCr) was 1.19 +/-0.20 mmol/L (mean +/- standard error), the activation energy (Ea) was 108.3+/-1.2 kJ/ mol, and the residual enzyme activity after heating at 45 degrees C for 20 min was 79.6+/-1.9%. On the other hand, octameric uMi-CK was focused at pI 7.1-7.9 and the dimeric forms were focused at pI 6.6, 6.7, 6.8, 6.9, and 7.0. Delysined forms were focused around pI 6.3, 6.4, 6.8, and 6.9. uMi-CK reacted with anti-sMi-CK antibodies, and the immune complexes were focused at pI 5.8. The Km value of uMi-CK for PCr was 1.07+/-0.03 mmol/L, Ea of uMi-CK was 110.0+/-0.9 kJ/mol, and the residual enzyme activity after heating at 45 degrees C for 20 min was 90.3+/-0.4%. The sMi-CK and uMi-CK were hybridized and the hybrid Mi-CK appeared at pI 6.78, 6.98, and 7.1-7.95. The pIs of the hybrid Mi-CK were between those of sMi-CK and uMi-CK. As described above, sMi-CK and uMi-CK were slightly different from each other with respect to the pI and some enzyme characteristics.

A comparative study of human muscle and brain creatine kinases expressed in Escherichia coli

We report the expression of the human muscle (CK-MM) and brain (CK-BB) creatine kinases in Escherichia coli. The proteins have been purified to apparent homogeneity and several of their physical and kinetic properties investigated. In the process, we have conclusively verified the correct DNA sequence of the genes encoding the respective isozymes, and determined the correct primary structure and mass of the gene products. Alignment of the primary sequences of these two enzymes shows 81% sequence identity with each other, and no obvious gross structural differences. However, Western blot analyses demonstrated the general lack of antigenic cross-reactivity between these isozymes. Preliminary kinetic analyses show the K(m) and k(cat) values for the creatine and MgATP substrates are similar to values reported for other isozymes from various tissues and organisms. The human muscle and brain CKs do not, however, exhibit the synergism of substrate binding that is observed, for example, in rabbit muscle creatine kinase.

Cloning, Escherichia coli expression, and phase-transition chromatography-based purification of recombinant rabbit heart mitochondrial creatine kinase

A cDNA clone of the mitochondrial sarcomeric creatine kinase cDNA was obtained by screening a rabbit heart library. This cDNA is characterized by a 1257-nucleotide open reading frame encoding a 419-amino-acid protein with a cleavable 39-amino-acid mitochondrial presequence (Accession No. AJ011334). This new member of the guanidino kinase family shows a high degree of sequence similarity with the other phosphagen kinases sequenced so far. The mature enzyme was efficiently expressed in Escherichia coli BL21(DE3) cells as a soluble octameric protein using the pET21 plasmid and purified by a three-step improved method including a final phase-transition chromatography.

Standardization of creatine kinase-MB (CK-MB) mass assays: the use of recombinant CK-MB as a reference material

BACKGROUND

The AACC assembled a committee to identify and validate a standard creatine kinase MB isoenzyme (CK-MB) material to improve the comparability of CK-MB mass assays.

METHODS

Three protocols were used. In protocol I, various CK-MB materials prepared in different matrices were screened as candidate standards. In protocol II, participating manufacturers calibrated their systems with concentrates of human heart CK-MB and then tested 20 patient samples to evaluate calibration bias. In protocol III, participating manufacturers calibrated their immunoassay systems using recombinant CK-MB2 (rCK-MB2) diluted into their respective sample diluents and measured 50 samples.

RESULTS

Candidate materials showed high recovery in stripped human serum, but bias improved only from 59% to 38%. These data led to the use of human heart CK-MB diluted in each manufacturer's sample diluent. This strategy reduced bias from 31% to 15%. Because human heart CK-MB is difficult to provide, a lyophilized source of CK-MB2 was identified. rCK-MB2 was shown by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, reversed-phase HPLC, intrinsic protein fluorescence, circular dichroism, agarose gel electrophoresis, immunoreactivity studies, high and low temperature stability, and reconstituted stability to be equivalent to human heart CK-MB. Calibration of immunoassay systems with rCK-MB2 added into each respective manufacturer's sample diluent showed a 13% between-manufacturer bias.

CONCLUSION

Lyophilized rCK-MB2 was determined suitable for use as a reference material for CK-MB mass assays.

Characterization of isoforms of human mitochondrial creatine kinase by isoelectric focusing

High enzyme activity of mitochondrial creatine kinase (creatine-N-phosphotransferase, mCK, EC 2.7.3.2) was detected in serum from a patient with advanced carcinoma of the rectum and its isoforms were characterized by means of isoelectric focusing (IEF). Three forms of mCK, membrane-bound (pI 6.9-7.0), octameric (pI 7.0-7.9) and dimeric (pI 6.7, 6.8, 6.9 and 7.0), were detected in the fresh serum. These three forms of mCK were converted to five dimeric isoforms, and these were characterized as one reduced form (pI 7.0) and four oxidized (pI 6.6, 6.7, 6.8 and 6.9) forms upon treatment with urea, hydrogen peroxide or 2-mercaptoethanol (2-ME). The C-terminal of the mCKs was concluded to be a lysine residue because the mCKs treated with carboxypeptidase B migrated to positions closer to the anode than did those not treated with carboxypeptidase B. Therefore, four bands were concluded to represent one reduced-delysined isoform (pI 6.4) and three oxidized-delysined isoforms (pI 6.1, 6.2 and 6.3). The broad octameric mCK band disappeared and a narrow band focused at pI 6.8-6.9 appeared upon probable delysination of the mCKs. Thus, the number of lysine residues at the C-terminal of the octamer was concluded to be variable due to variable catalysis by carboxypeptidase N in the plasma. mCKs seemed to be inactivated during conversion from a membrane-bound form to dimeric oxidized-delysined forms via the octameric, dimeric reduced and oxidized forms.

Immunochemical extraction and automated measurement of plasma creatine kinase MB isoenzyme and creatine kinase MB2 isoform

Measurement of creatine kinase MB (CK-MB) and its isoforms CK-MB2 and CK-MB1 are now applied in the diagnosis of acute myocardial infarction (AMI). The most common approach for analysis includes RIA, IRMA, and electrophoresis, all of which may be time-consuming. This study examines determination of CK-MB and CK-MB2 by a rapid immunochemical extraction method followed by an automated measurement for both analytes. The automated method was sensitive to 2 U/L, linear to 180 U/L, and gave excellent interassay precision (< 10% CV). Interference studies indicated that bilirubin, hemolysis, and lipemia caused analytical problems as did the presence of high activities of other CK isoenzymes, notably CK-MM and CK-BB, requiring dilution of samples prior to analysis. Application of immunochemical extraction gave a reference interval of CK-MB (0-2.5 U/L) and CK-MB2 (0.1-1.4 U/L) for blood donors (20-60 years), peak levels for ruled-out AMI patients of CK-MB (0.5-7.3 U/L) and CK-MB2 (0.3-4.9), peak levels for ruled-in AMI patients of CK-MB (80-174 U/L) and CK-MB2 (80-155 U/L). Coronary artery bypass patients (n = 24) and all trauma patients (n = 14) also demonstrated elevations in CK-MB and CK-MB2, whereas only five of the trauma patients demonstrated increased CK-MB by IRMA. In patients (n = 7) having increased total CK and normal CK-MB by IRMA, the extraction assay for CK-MB and CK-MB2 yielded increased values in all patients. This new approach to CK-MB and CK-MB2 analysis can be performed within 30 minutes of sample receipt.

Dissociation of creatine kinase under different denaturation conditions

Dissociation of dimeric creatine kinase under different denaturation conditions was investigated using the cleavable cross-linker 3, 3;-dithiobis(succinimidyl propionate). The results show that at low denaturant concentrations or at low denaturation temperatures the creatine kinase was mostly inactivated, but the enzyme was still either in the dimeric state or very slightly dissociated. It appears, therefore, that for several denaturation conditions, inactivation of the enzyme is not due to the dissociation of the active dimer.

Purification, crystallization and preliminary crystallographic analysis of bovine cytosolic brain-type creatine kinase

Creatine kinase (E.C. 2.3.7.2) is an important enzyme in energy metabolism which catalyzes the reversible transfer of a phosphoryl group between phosphocreatine and ADP to give ATP. Large quantities of a brain-type creatine kinase have been isolated from bovine photoreceptor cells and crystals suitable for X-ray diffraction analysis have been obtained by hanging-drop vapor diffusion. Crystals grow as tetragonal bipyramids in space group P43212 with cell dimensions a = b = 96.49, c = 108.42 A and diffract to at least 2.7 A resolution.

Origin of octameric creatine kinases

Mitochondrial creatine kinase (MiCK) occurs primarily as an octameric form localized in the mitochondrial intermembrane compartment in vertebrate tissues and echinoderm spermatozoa (both deuterostome groups). The octameric quaternary structure is thought to play important functional and enzyme targeting roles. We have found that the spermatozoa of the protostome polychaete Chaetopterus variopedatus contain three distinct isoenzymes of creatine kinase (CK) termed CK1, CK2 and CK3. CK3 appears to be present only in the sperm head/midpiece complex where mitochondria are restricted and has a subunit relative molecular mass (Mr) of 43.4 kDa. Gel permeation chromatography using Superdex 200HR showed that CK3 has a native Mr of 344.9 kDa indicating that this enzyme exists as an octamer. Electron micrographs of negatively stained CK3 preparations show structures which are virtually identical to those that have been seen for octameric vertebrate MiCK. The above observations show that CK3 from C. variopedatus displays great similarities to MiCKs from vertebrates and echinoderms. Octamerization of CK is not an advanced feature. The evolution of octameric subunit association is ancient and occurred prior to the divergence of protostomes and deuterostomes.

A novel autoantibody in paraneoplastic sensory-dominant neuropathy reacts with brain-type creatine kinase

We have previously reported on a novel autoantibody in a patient with paraneoplastic sensory-dominant neuropathy. This autoantibody immunostains the rat primary sensory system and reacts with a 47 kDa protein on immunoblotting. Here, we report on the isolation from rat spinal cord of a molecule that is recognized by this autoantibody. By ammonium sulfate cut and gel filtration, affinity and ion exchange chromatographies, the immunoreactive protein was purified to homogeneity and identified as brain-type creatine kinase (B-CK). Our study revealed that the autoantibody of the patient reacted with B-CK in the primary sensory system.

Degradation of myocardiac myosin and creatine kinase in rats given alkaline ionized water

Recently, the authors have shown that marked necrosis and fibrosis of myocardium were observed in rats given alkaline ionized water (AKW). To clarify the cause of myocardial lesions, the activities of myosin ATPase, actomyosin ATPase and creatine kinase (CK) in myocardium of rats given AKW at 15 weeks-old were compared with those in myocardium of rats given tap water (TPW). Furthermore, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) of myocardiac myosin and isoelectric focusing (IEF) of myocardiac CK were performed which revealed a distinct difference between AKW and TPW groups. The activities of myosin ATPase and actomyosin ATPase in the AKW group were higher than those in the TPW group, and these elevated activities were caused by the degradation of myosin in the AKW group judging from the SDS-PAGE pattern of myosin. On the other hand, the activity of CK in the AKW group was lower than that in the TPW group, and the IEF pattern of CK showed leakage of myocardiac CK. These results indicate that increases in actomyosin ATPase activity and myosin ATPase activity, plus the decrease in CK activity caused the disorder of coupled reaction in male rats given AKW at 15 weeks-old. It is concluded that this disorder of coupled reaction may cause marked myocardiac necrosis and fibrosis in rats given AKW.

Cytoplasmic creatine kinases from giant pandas

The muscle and brain creatine kinases of giant panda have been isolated and purified. The purified muscle and brain enzymes (MM and BB) are homogeneous on both the polyacrylamide gel electrophoresis in the presence and absence of SDS. Both enzymes are dimers, consisting of two identical subunits each with a molecular weight of 42,000 daltons. The characteristics of muscle and brain enzymes have been studied, respectively. The hybridized enzyme, MB, was prepared by hybridization of MM and BB. The kinetic parameters of MM, BB and MB were determined, respectively. The results from modification of SH groups show that the SH groups of panda creatine kinases are essential for their activity and among the all SH groups in the enzyme only one per subunit is essential for enzymatic activity.

The role of creatine kinase in inhibition of mitochondrial permeability transition

Cyclosporin A sensitive swelling of mitochondria isolated from control mouse livers and from the livers of transgenic mice expressing human ubiquitous mitochondrial creatine kinase occurred in the presence of both 40 microM calcium and 5 microM atractyloside which was accompanied by a 2.5-fold increase over state 4 respiration rates. Creatine and cyclocreatine inhibited the latter only in transgenic liver mitochondria. Protein complexes isolated from detergent solubilised rat brain extracts, containing octameric mitochondrial creatine kinase, porin and the adenine nucleotide translocator, were reconstituted into malate loaded lipid vesicles. Dimerisation of creatine kinase in the complexes and exposure of the reconstituted complexes to >200 microM calcium induced a cyclosporin A sensitive malate release. No malate release occurred with complexes containing octameric creatine kinase under the same conditions.

Mitochondrial creatine kinase interaction with phospholipid vesicles

The characteristics of the interaction of mitochondrial creatine kinase (mt-CK) with phospholipid vesicles are determined. The presence of negatively charged phospholipids is required to obtain a significant binding of mt-CK. The interaction seems to be largely of an electrostatic nature: it increases with increasing amounts of anionic phospholipid in liposomes and decreases when the ionic strength increases or when the pH of the medium is higher than the pI of mt-CK. We have compared the effects of various effectors used to solubilize mt-CK from the mitochondrial membrane on the binding of mt-CK to liposomes: the nucleotide substrates ATP and ADP have no influence, parahydroxymercuribenzoate, a negatively charged organomercurial compound, partially decreases mt-CK binding; and the anticancer agent adriamycin efficiently prevents mt-CK binding. As monitored by the increase in absorbance, mt-CK causes vesicle aggregation. A differential scanning calorimetry study, using dimyristoylphosphatidylcholine/dimyristoylphosphatidylglycerol vesicles, shows that mt-CK produces a decrease in the enthalpy variation without any change in the position of the calorimetric peak maximum. This suggests a partial disorganization of the phospholipid bilayer upon interaction with mt-CK.

Removal of endotoxin from recombinant protein preparations

OBJECTIVES

To develop an effective method to remove endotoxin from large scale E. coli recombinant protein purifications.

DESIGN AND METHODS

Triton X-114 phase separation, affinity chromatography utilizing immobilized polymyxin B or immobilized histidine, were used to remove endotoxin from purified preparations of recombinant CK-BB, CK-MB, CK-MM, myoglobin, and cardiac troponin I. Endotoxin levels were measured by a Limulus Amebocyte Lysate gel-clot assay. The immunoactivity of these protein preparations was determined by BIAcore analysis using a panel of in-house generated monoclonal antibodies and by a Stratus Fluorometric Analyzer. In the case of troponin I, the BIAcore was also utilized to measure troponin C interactions.

RESULTS

Phase separation with Triton X-114 was the most effective method in reducing the amount of endotoxin present in the protein preparations compared to either polymyxin B or histidine affinity chromatography. With Triton X-114, the reduction in endotoxin levels was greater than 99% and recovery of the proteins after endotoxin removal was greater than 90%. All three procedures for removing endotoxin had no deleterious effects on the immunoactivity of majority proteins when tested with a panel of monoclonal antibodies. Troponin I also retained its ability to bind to troponin C in the presence of Ca2+. Recombinant CK-BB and CK-MM which were expressed in the soluble fraction of E. coli cell lysates, contained significantly higher endotoxin levels than recombinant CK-MB, myoglobin and cardiac troponin I which were expressed in the form of inclusion bodies.

CONCLUSION

Of the three methods tested, Triton X-114 phase separation was the most effective way of removing endotoxin from recombinant proteins.

Copurification of vimentin, energy metabolism enzymes, and a MER5 homolog with nucleoside diphosphate kinase. Identification of tissue-specific interactions

Chromatography on immobilized antibodies specific to nucleoside diphosphate (NDP) kinase was utilized for affinity purification of this enzyme from detergent extracts of frog heart post-mitochondrial fractions. SDS-polyacrylamide gel electrophoresis analysis of eluates from these supports shows that five polypeptides co-purify with nucleoside diphosphate (NDP) kinase. Tryptic digests of each band were analyzed by mass spectrometric microsequencing. Data base searches by peptide mass matching and sequence homology led to the identification of these proteins as glyceraldehyde-3-phosphate dehydrogenase (40 kDa), creatine kinase (45 kDa), vimentin (55 kDa), pyruvate kinase (60 kDa), and a putative member of the antioxidant protein family (28 kDa). Distinct protein compositions were found in eluates of lung and liver extracts processed in a like manner. The 28-kDa band and vimentin were associated with NDP kinase from all tissues, but co-purification of pyruvate kinase was seen only in liver, while creatine kinase and glyceraldehyde-3-phosphate dehydrogenase were absent from eluates from lung and liver. The results suggest that while NDP kinase is associated with vimentin intermediate filaments and an antioxidant protein in most tissues, it interacts with energy metabolism enzymes in a tissue-specific manner.

Purification and characterization of human sarcomeric mitochondrial creatine kinase

In order to set the basis for detailed clinical investigations, mitochondrial creatine kinase (Mi-CK) was purified to homogeneity from human cardiac muscle. Biophysical characterization by SDS-PAGE, gel permeation chromatography and by electron microscopy of negatively stained single molecules demonstrated that, similar to other vertebrate Mi-CKs, human sarcomeric Mi-CK occurs in two different oligomeric forms, dimers and octamers, that are readily interconvertible. The apparent MTs of Mi-CK protomers, dimers and octamers were 43,600 +/- 800, 79,700 +/- 800 and 371,000 +/- 3000, respectively. In addition, isoelectric focussing proved to be a suitable technique for routinely distinguishing Mi-CK from cytosolic MM-CK and gave pl values of 8.30 +/- 0.04 and 7.44 +/- 0.04 for octameric and dimeric human sarcomeric Mi-CK. Circumstantial evidence suggests that both the highly symmetrical structure and the high pI value of Mi-CK octamers are crucial determinants for the physiological functions of this enzyme.

Complexes between kinases, mitochondrial porin and adenylate translocator in rat brain resemble the permeability transition pore

In vitro incubation of isolated hexokinase isozyme I or isolated dimer of mitochondrial creatine kinase with the outer mitochondrial membrane pore led to high molecular weight complexes of enzyme oligomers. Similar complexes of hexokinase and mitochondrial creatine kinase could be extracted by 0.5% Triton X-100 from homogenates of rat brain. Hexokinase and creatine kinase complexes could be separated by subsequent chromatography on DEAE anion exchanger. The molecular weight, as determined by gel-permeation chromatography, was approximately 400 kDa for both complexes. The Mr suggested tetramers of hexokinase (monomer 100 kDa) and creatine kinase (active enzyme is a dimer of 80 kDa). The composition of the complexes was further characterised by specific antibodies. Besides either hexokinase or creatine kinase molecules the complexes contained porin and adenylate translocator. It was possible to incorporate the complexes into artificial bilayer membranes and to measure conductance in 1 M KCI. The incorporating channels had a high conductance of 6 nS that was asymmetrically voltage dependent. The complexes were also reconstituted in phospholipid vesicles that were loaded with ATP. Complex containing vesicles retained ATP while vesicles reconstituted with pure porin were leaky. The internal ATP could be used by creatine kinase and hexokinase in the complex to phosphorylate external creatine or glucose. This process was inhibited by atractyloside. The hexokinase complex containing vesicles were furthermore loaded with malate or ATP that was gradually released by addition of Ca2+ between 100 and 600 microM. The liberation of malate or ATP by Ca2+ could be inhibited by N-methylVal-4-cyclosporin, suggesting that the porin translocator complex constitutes the permeability transition pore. The results show the physiological existence of kinase porin translocator complexes at the mitochondrial surface. It is assumed that such complexes between inner and outer membrane components are the molecular basis of contact sites observed by electron microscopy. Kinase complex formation may serve three regulatory functions, firstly regulation of the kinase activity, secondly stimulation of oxidative phosphorylation and thirdly regulation of the permeability transition pore.

Identification of human myocardial proteins separated by two-dimensional electrophoresis using an effective sample preparation for mass spectrometry

Peptide mass fingerprinting is a powerful tool for the identification of proteins separated by two-dimensional gel electrophoresis (2-DE). The identification of in-gel digested proteins by peptide mass fingerprinting was significantly improve in comparison to blot-digests by using a peptide-collecting device. This device allows the effective purification and concentration of enzymatic digests of low-intensity spots without expensive equipment and is described in detail. Sensitivity in the fmol range was demonstrated by unequivocal identification of bovine serum albumin after sodium dodecyl sulfate--polyacrylamide gel electrophoresis. Furthermore the high performance liquid chromatography pattern of in-gel digests indicated a 2- to 3-fold higher yield of the separated peptides. Therefore, a higher amount of the peptides was available to perform N-terminal sequencing. The identification of 16 proteins from a high-resolution 2-DE gel map of human myocardium tissue has been achieved by means of this technique. Three of these proteins were associated with changes in spot intensity with dilated cardiomyopathy.

Creatine kinase in trout male germ cells: purification, gene expression, and localization in the testis

High creatine kinase (CK) activity (16.5 +/- 7.6 IU/mg) is present in trout spermatozoa. In order to partly characterize the CK isozyme predominantly present in sperm and to study the expression of this protein in spermatogenesis, we purified to homogeneity a CK (s-CK) from trout sperm, by nitrogen cavitation followed by two chromatography steps (DEAE-Trisacryl and Blue Sepharose). Specific antisera to 5-CK were developed. A cDNA encoding for a CK named TCK1, and whose transcript shows enhanced testicular expression, was previously isolated from trout testis (Garber et al., 1990: Biochim Biophys Acta 1087:256-258). A CK subunit expressed in vitro by this cDNA cross-reacts with anti-s-CK. A 21-amino-acid residue sequence near the N-terminus of s-CK is identical to the cDNA-derived sequence of TCK1, which is unlike any previously reported CK sequence. Using in situ hybridization, the TCK1 mRNA was detectable in primary and secondary spermatocytes and in early spermatids. Immunohistochemical staining of testis and various organs revealed that s-CK was confined to testis and, in this organ, to late spermatids and spermatozoa. In gill, some cells exhibited a positive signal, but another study rules out the presence of s-CK in this organ (Garber et al., 1990: Biochim Biophys Acta 1087:256-258). These results demonstrate that s-CK/TCK1 is a germ cell-specific protein, the transcription of which starts in meiotic germ cells, while translation starts in late spermatids.

Rabbit muscle creatine kinase: consequences of the mutagenesis of conserved histidine residues

Creatine kinase (CK; EC 2.7.3.2) catalyzes the reversible conversion of creatine and MgATP to phosphocreatine and MgADP. In the absence of an X-ray crystal structure, we have used the sequence homology of creatine kinases and other guanidino kinases from a variety of sources to identify the conserved histidine residues in rabbit muscle CK, as well as to try to pinpoint a reactive histidine that has been implicated in the active site. This residue has been proposed to act as a general acid/base catalyst assisting in the phosphoryl transfer mechanism [Cook et al. (1981) Biochemistry 20, 1204-1210]. There are 17 histidine residues in rabbit muscle CK, and of these, only five have been conserved in all guanidino kinase sequences published to date [Mühlebach et al. (1994) Mol. Cell. Biochem. 133, 245-62]. In rabbit muscle CK, these residues are H96, H105, H190, H233, and H295. We have carried out site-specific mutagenesis of these five histidine residues, replacing each with an asparagine. Each of these mutants exhibited enzymatic activity but to varying degrees. The H105N, H190N, and H233N mutants displayed specific activities similar to that of the wild-type enzyme. H96N has high activity, but appears to be quite unstable, losing catalytic activity upon cell lysis by sonication and/or chromatographic steps involved in purification. H295N shows a significantly reduced catalytic activity relative to the native enzyme, due to marked decreases in kcat and the affinities for both substrates. Each of the five mutants is inactivated by diethyl pyrocarbonate (DEP), and inactivation is reversible upon incubation with hydroxylamine. However, only H295N shows a dramatically reduced rate of inactivation relative to native CK, consistent with H295 being the residue modified by DEP in the native enzyme. These intriguing results indicate that four of the conserved histidines (H96, H105, H295, and H233) are not essential for activity, and while H295 may be at the active site of CK, it is unlikely to play the role of a general acid/base catalyst.

Harvest protocol to reduce variability of soluble enzyme yield from cultured cells

Many aspects of physiology and gene regulation can be studied by examining the levels of enzymes harvested from cultured cells. We found that the yield from cultured cells of two different cytosolic enzymes, creatine kinase and the common reporter gene product chloramphenicol acetyltransferase (CAT), could be highly variable despite superficially identical harvest procedures. Analysis of multiple harvest and assay parameters disclosed that fluctuations in enzyme yield were correlated with the time cells that were allowed to remain in an EDTA-containing buffered saline solution prior to scraping from the dishes with a rubber policeman. The highest and most consistent yields were obtained when the cells were allowed to remain in the solution for 6-10 min before scraping: this protocol has cut variability approximately by a factor of three.

Creatine kinase isoenzyme profiles in the plasma of the domestic fowl (Gallus domesticus): effects of acute heat stress

Creatine kinase isoenzyme activities in extracts of plasma, skeletal muscle, heart and brain tissue of domestic fowls were separated by anion exchange chromatography and tissue specific distributions of the isoenzyme designated MM-CK, BB-CK1 and BB-CK2 were demonstrated. The muscle isoenzyme (MM-CK) was the predominant form in plasma (99 per cent) and its activity increased in response to an episode of acute heat stress.

Re-evaluation of the structure and physiological function of guanidino kinases in fruitfly (Drosophila), sea urchin (Psammechinus miliaris) and man

Purification and biophysical characterization of mitochondrial creatine kinase (Mi-CK) from sperm of the sea urchin Psammechinus miliaris, as well as gel-permeation chromatography of human heart Mi-CK demonstrate that these two Mi-CK isoenzymes form highly symmetrical octameric molecules with an M(r) of approx. 350,000, a value similar to that found for all other Mi-CK isoenzymes investigated so far. The absolute evolutionary conservation of this oligomeric form from sea urchins to mammals points both to its essentiality for Mi-CK function and to an important role of octameric Mi-CK in the energy metabolism of tissues and cells with high and fluctuating energy demands. To investigate whether a similar physiological principle also operates in an even more distantly related animal phylum, the arginine kinase (ArgK) isoenzyme system of Drosophila flight muscle was investigated with two independent subcellular fractionation procedures and subsequent analysis of the fractions by SDS/PAGE, immunoblotting and native isoenzyme electrophoresis. In contrast with a previous report [Munneke and Collier (1988) Biochem. Genet. 26, 131-141], strong evidence against the occurrence of a Mi-ArgK isoenzyme in Drosophila was obtained. The findings of the present study are discussed in the context of CK and ArgK function in general and of structural and bioenergetic differences between vertebrate striated muscles and arthropod flight muscles.

Multienzyme control serum (Seraclear-HE) containing human enzymes from established cell lines and other sources. 1: Preparation and properties

We have developed a new multienzyme control serum, Seraclear-HE, which was designed to function not only as an accuracy and precision control serum but also as an intermethod calibrator for unifying interlaboratory clinical enzyme data in terms of reference method values. Seraclear-HE contains as analytes the following enzymes of human origin only: aspartate aminotransferase (AST, EC 2.6.1.1) and lactate dehydrogenase (LD, EC 1.1.1.27) from erythrocytes; alanine aminotransferase (ALT, EC 2.6.1.2) from a hepatoma cell line; alkaline phosphatase (ALP, EC 3.1.3.1) from an amnion cell line; creatine kinase (CK, EC 2.7.3.2) from an embryo kidney cell line; gamma-glutamyltransferase (GGT, EC 2.3.2.2) from a macrophage cell line; and amylase (AMY, EC 3.2.1.1) from urine and saliva. The seven partly purified enzymes were lyophilized in partially delipidated human serum containing sucrose (50 g/L), pyridoxal 5'-phosphate (30 mmol/L), and other stabilizers. The material is stable for at least 2 years at temperatures < or = 10 degrees C. For two concentrations of this preparation, reference method values (mainly International Federation of Clinical Chemistry and Japan Society of Clinical Chemistry) obtained at both 30 degrees C and 37 degrees C are assigned.

Enhancing protein solubilization with nondetergent sulfobetaines

A significant increase in the yield of protein extraction by the addition of sulfobetaine-type mild solubilization agents is shown for microsomal membrane proteins and proteins from lyophilized platelets, with a maximum increase in yield of up to 100%. These agents are also applied to native isoelectric focusing in immobilized pH gradients. The absence of significant denaturation induced by these solubilizers is shown for creatine kinase.