Structural proteins of dogfish skeletal muscle

Influence of process variables on the hydrolysis of shark muscle protein / Influencia de las variables de proceso en la hidrólisis de proteína del músculo de tiburón

Muscle tissue from the spiny dogfish ( Squalus acanthias) was enzymatically hydrolysed using a bacterial endopeptidase. The influence of the process variables (temperature, pH, enzyme/ substrate ratio and reaction time) was investigated with regards to the extent of proteolytic degra dation and the recovery of soluble nitrogen from the substrate. Maximum significant nitrogen recovery (NR) was found to be 76.2%, in a 2 h proteolytic reaction. Optimum conditions were 55 °C, pH 8.0 and an enzyme/substrate ratio of 40 mg enzyme/g minced shark muscle (wet weight basis). Under these conditions, a degree of hydrolysis (DH) of 18.6% was obtained. A linear corre lation ( R2 = 0.99) was found to exist between the two measured parameters, NR and DH.

Anti-sulfonylbenzoate antibodies as a tool for the detection of nucleotide-binding proteins for functional proteomics

Proteins that bind ATP and GTP are important cellular components. We developed an immunological approach to selectively tag nucleotide-binding proteins based on the use of 5'-[4-(fluorosulfonyl)benzoyl]adenosine and 5'-[4-(fluorosulfonyl)benzoyl]guanosine affinity tags and an antibody against 4-(sulfonyl)benzoate. Detection follows affinity labeling, gel electrophoresis, and ester bond cleavage to expose the epitope. Trial analyses of labeled proteins from lymphoid cells identified multiple ATP-binding proteins, including chaperones, actin, kinases, an RNA splicing factor, a membrane ATPase, and ATP synthase.

Characterization of the single tyrosine containing troponin C from lungfish white muscle. Comparison with several fast skeletal muscle troponin C's from fish species

Troponin C molecules from fast skeletal muscle of the following fish species (trout, whiting, lungfish, tilapia, and cod) have been purified to homogeneity. Upon binding of Ca2+ or Mg2+, lungfish troponin C is the only troponin C from fish white muscle to show the typical increase of tyrosine fluorescence emission quantum yield reported for rabbit fast skeletal muscle troponin C. The increase of tyrosine fluorescence signal occurring upon Ca2+ and Mg2+ titration of lungfish troponin C has been used to determine the corresponding affinity constants. With K(Ca) = 7.0 10(7) M-1 and K(Mg) = 3.6 10(3) M-1, the sites probed by the tyrosine residue of lungfish troponin C are typical of the COOH-terminal domain of fast skeletal troponin C's. The amino acid sequencing of the tyrosine containing tryptic peptides has allowed us to position the single tyrosine residue at position 7 in the Ca2+ binding loop of the third site, in identical position to Tyr109 of troponin C from rabbit fast skeletal muscle. Metal ion binding studies followed by intrinsic fluorescence or Tb3+ luminescence indicate that the conformation of the structural domain of lungfish troponin C with one metal ion bound is close to the physiological conformation of this domain.

Determination of the Ca2+ and Mg2+ affinity constants of troponin C from eel skeletal muscle and positioning of the single tryptophan in the primary structure

The complete amino acid sequence of troponin C (ETnC) from the white muscle of the European eel has been determined by Edman degradation procedures. Its single tryptophan residue is situated in helix H at amino acid position 152 of the aligned sequence; the tryptophan is the first residue on the C-terminal side of Ca2+ binding loop IV. The increase of tryptophan fluorescence emission intensity occurring upon titration of ETnC with Ca2+ has been used to determine the affinity constants of ETnC for Ca2+. The calculated affinity of ETnC for Ca2+ results in a K(Ca) of 1.3 10(7) M-1, typical of the Ca(2+)-Mg2+ sites of the second domain of fast skeletal muscle TnCs. Moreover, a direct competition between Ca2+ and Mg2+ was also observed. The calculated affinity of ETnC for Mg2+ is K(Mg) = 1.2 10(3) M-1. In order to probe the affinity constants of the Ca2+ binding sites of the regulatory domain, ETnC was labelled with dansylaziridine (Danz). The Danz fluorescent signal was used to estimate the affinity constants of ETnC-Danz for Ca2+ and also for Mg2+ (assuming a competitive behaviour between these two metal ions). The calculated affinity constants are K(Ca) = 9.4 10(5) M-1 and K(Mg) = 2.0 10(2) M-1, respectively. These values are typical of the Ca(2+)-specific sites of the regulatory domain of fast skeletal muscle TnCs.

The purification of a unique calcium-binding protein from Morris hepatoma 5123 tc

A heat-stable Ca2+-binding protein was purified to homogeneity from Morris hepatoma 5123 tc. It had an apparent molecular weight of 11 000, and isoelectric point of 3.9, and bound two atoms of calcium per molecule of protein. The spectral and amino acid analysis indicated the tumour protein to be similar to the parvalbumins. This protein has been shown to be absent in liver.

Molar absorptivity and A1%1 cm values for proteins at selected wavelengths of the ultraviolet and visible regions--XVIII

A table of molar absorptivity and A1cm1% values for more than 180 proteins is given. The conditions used to obtain these values and references to the original literature are also'given.

Experimental corticosteroid myopathy: effect on myofibrillar ATPase activity and protein degradation

Corticosteroid myopathy was studied in young, mature New Zealand white rabbits given daily injections of betamethasone (0.3 mg/kg body weight/day) for two weeks. Control rabbits were pair-fed and received saline injections. Bethamethasone treatment caused significant wasting of type 2 gluteus medius and psoas muscles but did not cause any atrophy of type 1 soleus and gluteus minimus muscles. The Mg2+- and Ca2+-activated myofibrillar ATPase activities of the corticosteroid-treated rabbits did not differ from controls despite a 30% reduction in muscle wet weight and pronounced reduction in cross-sectional area of fibers. SDS-polyacrylamide gel electrophoresis profiles of myofibrillar proteins did not differ quantitatively or qualitatively between experimental and control rabbits. Studies of net muscle protein degradation (using 3H-leucine) in betamethasone-treated and control rabbits indicate that both type 1 and type 2 muscle fiber proteins are degraded several times faster in the corticosteroid-treated group. This suggests that a compensatory mechanism exists for those type 1 and mixed fiber type muscles which have increased degradation but do not undergo wasting.

Beef muscle troponin: evidence for multiple forms of troponin-T

A method is described for the purification of troponin from beef skeletal muscle. The resultant preparation differs from the troponin of rabbit skeletal muscle in that it contains at least two forms of the tropomyosin-binding component, Troponin-T: these are designated as the 37 000 and 40 000 dalton forms of Troponin-T on the basis of sodium dodecyl sulphate gel electrophoresis. Either of these Troponin-T forms may be used to reconstitute troponin by mixing with the appropriate amounts of the calcium-binding (Troponin-C) and and actomyosin ATPase-inhibitory (Troponin-I) components. These reconstituted troponins are shown to interact with tropomyosin and also to confer full calcium sensitivity on actomyosin ATPase. Despite the existence of proteolysis in troponin preparations, the experimental evidence indicates that the smaller form of Troponin-T is not derived from the 40 000 dalton species by limited degradation. Although both species of Troponin-T have been found routinely in troponin from beef skeletal muscle, only the larger form is detected in troponin preparations from beef cardiac muscle. Further studies are required in order to clarify the functional significance and differential distribution of these multiple forms of Troponin-T.