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Chang FMJ, Lauber MA, Running WE, Reilly JP, Giedroc DP. Ratiometric pulse-chase amidination mass spectrometry as a probe of biomolecular complex formation. Anal Chem 2011; 83:9092-9. [PMID: 22007758 DOI: 10.1021/ac202154r] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Selective chemical modification of protein side chains coupled with mass spectrometry is often most informative when used to compare residue-specific reactivities in a number of functional states or macromolecular complexes. Herein, we develop ratiometric pulse-chase amidination mass spectrometry (rPAm-MS) as a site-specific probe of lysine reactivities at equilibrium using the Cu(I)-sensing repressor CsoR from Bacillus subtilis as a model system. CsoR in various allosteric states was reacted with S-methyl thioacetimidate (SMTA) for pulse time, t, and chased with excess of S-methyl thiopropionimidate (SMTP) (Δ = 14 amu), quenched and digested with chymotrypsin or Glu-C protease, and peptides were quantified by high-resolution matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry and/or liquid chromatography electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS). We show that the reactivities of individual lysines from peptides containing up to three Lys residues are readily quantified using this method. New insights into operator DNA binding and the Cu(I)-mediated structural transition in the tetrameric copper sensor CsoR are also obtained.
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Affiliation(s)
- Feng-Ming James Chang
- Department of Chemistry, Indiana University, 800 East Kirkwood Avenue, Bloomington, Indiana 47405-7102, USA
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2
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Jaren OR, Kranz JK, Sorensen BR, Wand AJ, Shea MA. Calcium-induced conformational switching of Paramecium calmodulin provides evidence for domain coupling. Biochemistry 2002; 41:14158-66. [PMID: 12450379 DOI: 10.1021/bi026340+] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Calmodulin (CaM) is an intracellular calcium-binding protein essential for many pathways in eukaryotic signal transduction. Although a structure of Ca(2+)-saturated Paramecium CaM at 1.0 A resolution (1EXR.pdb) provides the highest level of detail about side-chain orientations in CaM, information about an end state alone cannot explain driving forces for the transitions that occur during Ca(2+)-induced conformational switching and why the two domains of CaM are saturated sequentially rather than simultaneously. Recent studies focus attention on the contributions of interdomain linker residues. Electron paramagnetic resonance showed that Ca(2+)-induced structural stabilization of residues 76-81 modulates domain coupling [Qin and Squier (2001) Biophys. J. 81, 2908-2918]. Studies of N-domain fragments of Paramecium CaM showed that residues 76-80 increased thermostability of the N-domain but lowered the Ca(2+) affinity of sites I and II [Sorensen et al. (2002) Biochemistry 41, 15-20]. To probe domain coupling during Ca(2+) binding, we have used (1)H-(15)N HSQC NMR to monitor more than 40 residues in Paramecium CaM. The titrations demonstrated that residues Glu78 to Glu84 (in the linker and cap of helix E) underwent sequential phases of conformational change. Initially, they changed in volume (slow exchange) as sites III and IV titrated, and subsequently, they changed in frequency (fast exchange) as sites I and II titrated. These studies provide evidence for Ca(2+)-dependent communication between the domains, demonstrating that spatially distant residues respond to Ca(2+) binding at sites I and II in the N-domain of CaM.
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Affiliation(s)
- Olav R Jaren
- Department of Biochemistry, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242-1109, USA
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3
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Apuy JL, Chen X, Russell DH, Baldwin TO, Giedroc DP. Ratiometric pulsed alkylation/mass spectrometry of the cysteine pairs in individual zinc fingers of MRE-binding transcription factor-1 (MTF-1) as a probe of zinc chelate stability. Biochemistry 2001; 40:15164-75. [PMID: 11735399 DOI: 10.1021/bi0112208] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Metal-response element (MRE)-binding transcription factor-1 (MTF-1) is a zinc-regulated transcriptional activator of metallothionein (MT) genes in mammalian cells. The MRE-binding domain of MTF-1 (MTF-zf) has six canonical Cys(2)-His(2) zinc finger domains that are distinguished on the basis of their apparent affinities for zinc and their specific roles in MRE-binding. In this paper, pulsed alkylation of the zinc-liganding cysteine thiolate pairs with the sulfhydryl-specific alkylating reagent d(5)-N-ethylmaleimide (d(5)-NEM) is used as a residue-specific probe of the relative stabilities of the individual zinc finger coordination complexes in Zn(6) MTF-zf. A chase with excess H(5)-N-ethylmaleimide (H(5)-NEM) to fully derivatize MTF-zf concomitant with complete proteolysis, followed by MALDI-TOF mass spectrometry allows quantitation of the mole fraction of d(5),d(5)-, d(5),H(5)-, and H(5),H(5)-NEM derivatized peptides corresponding to each individual zinc finger domain as a function of d(5)-NEM pulse time. This experiment establishes the hierarchy of cysteine thiolate reactivity in MTF-zf as F5 > F6 >> F1 > F2 approximately F3 approximately F4. The apparent second-order rate of reaction of F1 thiolates is comparable to that determined for the DNA binding domain of Sp1, Zn(3) Sp1-zf, under identical solution conditions. The reactivities of all Cys residues in MTF-zf are significantly reduced when bound to an MREd-containing oligonucleotide. An identical experiment carried out with Zn(5) MTF-zf26, an MTF-zf domain lacking the N-terminal F1 zinc finger, reveals that MTF-zf26 binds to the MREd very weakly, and is characterized by strongly increased reactivity of nonadjacent F4 thiolates. These findings are discussed in the context of existing models for metalloregulation by MTF-1.
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Affiliation(s)
- J L Apuy
- Department of Biochemistry and Biophysics, Center for Advanced Biomolecular Research, Texas A&M University, College Station, Texas 77843-2128, USA
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4
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Moore CP, Rodney G, Zhang JZ, Santacruz-Toloza L, Strasburg G, Hamilton SL. Apocalmodulin and Ca2+ calmodulin bind to the same region on the skeletal muscle Ca2+ release channel. Biochemistry 1999; 38:8532-7. [PMID: 10387100 DOI: 10.1021/bi9907431] [Citation(s) in RCA: 105] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The skeletal muscle Ca2+ release channel (RYR1) is regulated by calmodulin in both its Ca2+-free (apocalmodulin) and Ca2+-bound (Ca2+ calmodulin) states. Apocalmodulin is an activator of the channel, and Ca2+ calmodulin is an inhibitor of the channel. Both apocalmodulin and Ca2+ calmodulin binding sites on RYR1 are destroyed by a mild tryptic digestion of the sarcoplasmic reticulum membranes, but calmodulin (either form), bound to RYR1 prior to tryptic digestion, protects both the apocalmodulin and Ca2+ calmodulin sites from tryptic destruction. The protected sites are after arginines 3630 and 3637 on RYR1. These studies suggest that both Ca2+ calmodulin and apocalmodulin bind to the same or overlapping regions on RYR1 and block access of trypsin to sites at amino acids 3630 and 3637. This sequence is part of a predicted Ca2+ CaM binding site of amino acids 3614-3642 [Takeshima, H., et al. (1989) Nature 339, 439-445].
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Affiliation(s)
- C P Moore
- Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, Texas 77030, USA
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5
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Leclerc L'Hostis E, Leclerc L, Haiech J, Poyart C, Marden MC. Heme-CO binding to tryptophan-containing calmodulin mutants. BIOCHIMICA ET BIOPHYSICA ACTA 1996; 1313:209-16. [PMID: 8898856 DOI: 10.1016/0167-4889(96)00091-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The binding of heme-CO to genetically engineered calmodulin containing a single tryptophan residue has been studied. A tryptophan residue was integrated at one of five positions: 26 or 62 of the N-terminal, 81 in the central helix, or 99 or 135 of the C-terminal. As for the wild type, the mutant calmodulins bind four molecules of heme-CO with an average affinity of 1 microM. (i) Homotropic effect. The quenching of the tryptophan fluorescence by energy transfer to the hemes indicates that there is no preference between the N- or C-terminal pockets for heme binding. The quenching is less than expected for a binomial distribution of four sites. This could indicate a lower energy transfer rate due to a specific orientation factor. The weak quenching as a function of the number of hemes bound may also reveal a cooperativity in the heme binding; the data can be simulated assuming two pairs of sites, where each pocket shows a cooperative binding for two hemes. (ii) Heterotropic effect. As observed for the wild type, addition of melittin does not displace the hemes from the mutant calmodulins; the affinity of heme-CO for the calmodulin.melittin complex is higher than that for calmodulin alone. The affinity of heme-CO for native calmodulin is also higher in the presence of trifluoperazine.
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Affiliation(s)
- E Leclerc L'Hostis
- Institut National de la Santé et de la Recherche Médicale, Unité 299, Hôpital de Bicêtre, Le Kremlin-Bicêtre, France
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6
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Shea MA, Verhoeven AS, Pedigo S. Calcium-induced interactions of calmodulin domains revealed by quantitative thrombin footprinting of Arg37 and Arg106. Biochemistry 1996; 35:2943-57. [PMID: 8608132 DOI: 10.1021/bi951934g] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Calcium-dependent conformational states of calmodulin (CaM) were probed by thrombin to determine quantitative differences in the susceptibility of two bonds: Arg37-Ser38 (R37-S38, near site I in the N-terminal domain) and Arg106-His107 (R106-H107, near site III in the C-terminal domain). Quantitative thrombin footprinting of a discontinuous equilibrium calcium titration of wild-type calmodulin showed that the R37-S38 bond of the apoprotein was cleaved at a barely detectable level while the R106-H107 bond was maximally susceptible. Calcium binding to sites III and IV monotonically protected R106-H107 from proteolysis; concomitantly, the susceptibility of R37-S38 increased. However, calcium binding to sites I and II protected R37-S38 from cleavage, yielding a peaked biphasic profile composed of equal and opposite transitions. Both bonds were fully protected when calmodulin was saturated with calcium. Susceptibility profiles resolved from the fractional abundance of primary cleavage products (peptides 1-37, 38-148, 1-106, 107-148) were interpreted as directly reflecting calcium-induced conformational changes in whole calmodulin; free energies of calcium binding and cooperativity were estimated. Secondary cleavage was never observed; both R37 and R106 were sites of thrombinolysis in whole calmodulin only. In studies of E140Q-CaM (having a mutation in site IV), the susceptibility of R37-S38 decreased monotonically. Thus, the biphasic character of cleavage of R37 in helix B was not intrinsic to that domain but depended on propagation of effects of calcium-induced changes in the C-terminal domain. The observed patterns of susceptibility indicated that partially saturated wild-type calmodulin adopts at least one intermediate conformation whose structure is determined by calcium-mediated interactions between the domains.
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Affiliation(s)
- M A Shea
- Department of Biochemistry, University of Iowa College of Medicine, Iowa City, 52242-1109, USA
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7
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Aizawa M, Damrongchai N, Kobatake E. Protein supramolecular systems for molecular information processing. ACTA ACUST UNITED AC 1996. [DOI: 10.1016/0968-5677(96)00029-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
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8
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Török K, Trentham DR. Mechanism of 2-chloro-(epsilon-amino-Lys75)-[6-[4-(N,N- diethylamino)phenyl]-1,3,5-triazin-4-yl]calmodulin interactions with smooth muscle myosin light chain kinase and derived peptides. Biochemistry 1994; 33:12807-20. [PMID: 7947686 DOI: 10.1021/bi00209a012] [Citation(s) in RCA: 83] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The mechanism of the interactions of 2-chloro-(epsilon-amino-Lys75)-[6-[4-(N,N-diethylamino)phenyl]- 1,3,5-triazin-4-yl]calmodulin (TA-calmodulin) with smooth muscle myosin light-chain kinase (MLCK) and two 17-residue peptides, Ac-R-R-K-W-Q-K-T-G-H-A-V-R-A-I-G-R-L-CONH2 (Trp peptide) and Tyr peptide, in which W is replaced by Y, were studied by measurements of equilibrium and transient fluorescence changes in the nanomolar range. Most reactions were carried out in 100 microM CaCl2 at ionic strength 0.15 M, pH 7.0, and 21 degrees C. In each case association of MLCK or peptide to TA-calmodulin could be described by a two-step process, a bimolecular step and an isomerization. In the case of the interaction between TA-calmodulin and Tyr peptide it was shown that the isomerization involved the binary complex of TA-calmodulin and Tyr peptide as opposed to an isomerization of either TA-calmodulin or Tyr peptide in isolation. These distinctions depended in part on development for transient kinetic experiments of a general theory to quantify relative phase amplitudes in two-step mechanisms. The kinetics for all three association reactions were then interpreted in terms of a bimolecular association (rate constants k+1 and k-1) followed by an isomerization of the binary complex (rate constants k+2 and k-2). For the interaction of TA-calmodulin and Tyr peptide, values of the rate constants are k+1, 8.8 x 10(8) M-1 s-1; k-1, 5.7 s-1; k+2, 0.38 s-1; and k-2, 0.65 s-1. The fluorescence intensities (lambda ex 365 nm, lambda ex 365 nm, lambda em > 400 nm) of TA-calmodulin, the initial binary complex of TA-calmodulin and Tyr peptide, and the isomerized binary complex are in the ratio 1:2.8:1.3. Analogous mechanisms were found for TA-calmodulin binding to Trp peptide and to MLCK, but values for the rate constants and relative fluorescence intensities of the binary complexes were generally not so completely defined. Values for the Trp peptide and MLCK, respectively, are k+1, 8.8 x 10(8) M-1 s-1 and 1.1 x 10(8) M-1 s-1; (k+2 + k-2), 0.97 s-1 and 1.3 s-1; and k-1k-2/(k+2 + k-2), 0.0079 s-1 and 0.025-0.056 s-1. Equilibrium dissociation constants (Kd) for interactions of TA-calmodulin and targets determined from these data are Tyr peptide, 4.1 nM; Trp peptide, 0.011 nM; and MLCK, 0.23-0.51 nM.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- K Török
- National Institute for Medical Research, Mill Hill, London, United Kingdom
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9
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Huque ME, Vogel HJ. Carbon-13 NMR studies of the lysine side chains of calmodulin and its proteolytic fragments. JOURNAL OF PROTEIN CHEMISTRY 1993; 12:695-707. [PMID: 8136020 DOI: 10.1007/bf01024928] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The pH-titration and dynamic behaviour of the seven lysine side chains in bovine calmodulin were studied by carbon-13 NMR. The amino groups of the calcium saturated protein and its proteolytic fragments TR1C (1-75) and TR2C (78-148) were dimethylated with carbon-13 labeled formaldehyde; this modification did not alter the protein's structure or its ability to activate the enzyme cyclic nucleotide phosphodiesterase. Tentative assignments for 5 out of the 7 dimethyl lysine resonances could be obtained by comparing spectra of the fully and partially modified protein, with those of the proteolytic fragments. The pKa values measured for calcium saturated calmodulin ranged between 9.5 (Lys 75) and 10.2 (Lys 13); two residues (Lys 94 and Lys 13) showed a biphasic titration curve suggesting their possible involvement in ion-pairs. The dynamic behavior of the lysine side chains was deduced from spin lattice relaxation measurements. All side chains were flexible and this was not influenced by the removal of calcium, or the addition of the calmodulin antagonist trifluoperazine. The latter data suggest that the lysine side chains are not directly involved in calmodulin's target binding sites.
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Affiliation(s)
- M E Huque
- Department of Biological Sciences, University of Calgary, Canada
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10
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11
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Matsuura I, Kimura E, Tai K, Yazawa M. Mutagenesis of the fourth calcium-binding domain of yeast calmodulin. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(19)38647-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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12
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Robson KJ, Gamble Y, Acharya KR. Molecular modelling of malaria calmodulin suggests that it is not a suitable target for novel antimalarials. Philos Trans R Soc Lond B Biol Sci 1993; 340:39-53. [PMID: 8099744 DOI: 10.1098/rstb.1993.0047] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The recent cloning and sequencing of many calmodulin genes permits alignment of DNA and protein sequences, as well as structural comparison based on homology modelling. The crystal structure of calmodulin places the four Ca(2+)-binding domains in a dumbbell-like configuration, with a large hydrophobic cleft in each half of the molecule. Calmodulin from Plasmodium falciparum has a high level of sequence identity (89%) with its mammalian counterpart. However, a lower degree of sequence conservation is observed among calmodulins from other lower eukaryotes. Potentially important differences in calmodulin sequences involve amino acids with side-chains forming the hydrophobic clefts as well as in the central helix; these differences could alter interactions with small hydrophobic molecules such as chloroquine and with enzymes modulated by calmodulin. Our modelling studies suggest that neither of the antimalarials examined (chloroquine and quinine) bind tightly to calmodulin. We conclude that the differences between host and parasite calmodulins are insufficient to merit this protein being chosen as a realistic target for antimalarial drug design. By contrast, our sequence comparisons reveal that the fungal calmodulins are significantly divergent from those of higher eukaryotes suggesting that at least in these species, calmodulin might be a target for novel antimycotic drugs.
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Affiliation(s)
- K J Robson
- MRC Molecular Haematology Unit, University of Oxford, John Radcliffe Hospital, Headington, U.K
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13
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Dwyer L, Crocker P, Watt D, Vanaman T. The effects of calcium site occupancy and reagent length on reactivity of calmodulin lysyl residues with heterobifunctional aryl azides. Mapping interaction domains with specific calmodulin photoprobe derivatives. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(18)41716-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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14
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Abstract
Acetaldehyde covalently binds to tubulin to form stable and unstable adducts. Although tubulin has numerous lysine residues available to react with acetaldehyde, a key highly reactive lysine (HRL) on the alpha chain appears to be a preferential target for stable binding. The HRL residue is available for selective binding when tubulin is in the free (dimer) state but not when it is in the polymerized (microtubule) state. Stable binding of acetaldehyde to the HRL residue markedly inhibits tubulin assembly into microtubules, whereas stable binding to other residues (bulk adducts) has little influence on assembly. Substoichiometric stable binding of acetaldehyde to the HRL is sufficient to inhibit polymerization, via direct interference of tubulin dimer-dimer interactions, and an HRL adduct on only one out of 20 tubulin molecules can totally inhibit polymerization. These findings, along with our previous studies demonstrating impaired microtubule-dependent protein trafficking pathways in livers of ethanol-fed animals, indicate that low acetaldehyde concentrations, formed during ethanol oxidation in vivo, could generate sufficient amounts of HRL adducts on the alpha chain of tubulin in cellular systems to alter microtubule formation and function. In addition to alpha-tubulin, calmodulin and actin have also been found to have enhanced reactivity toward acetaldehyde. Thus, a general hypothesis to describe cellular injury induced by acetaldehyde adducts can be formulated: during ethanol oxidation, acetaldehyde forms stable adducts via binding to reactive lysine residues of preferential target proteins, resulting in selective functional impairment of these proteins and ultimately leading to cellular injury.
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Affiliation(s)
- D J Tuma
- Liver Study Unit, Department of Veterans Affairs Medical Center, Omaha, Nebraska 68105
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15
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Tomasselli AG, Howe WJ, Hui JO, Sawyer TK, Reardon IM, DeCamp DL, Craik CS, Heinrikson RL. Calcium-free calmodulin is a substrate of proteases from human immunodeficiency viruses 1 and 2. Proteins 1991; 10:1-9. [PMID: 2062825 DOI: 10.1002/prot.340100102] [Citation(s) in RCA: 31] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Calcium-free calmodulin-(CaM) is rapidly hydrolyzed by proteases from both human immunodeficiency viruses (HIV) 1 and 2. Kinetic analysis reveals a sequential order of cleavage by both proteases which initiates in regions of the molecule known from X-ray crystallographic analysis of Ca2+/CaM to be associated with calcium binding. Although HIV-1 and HIV-2 proteases hydrolyze two bonds in common, the initial site of cleavage required for subsequent events differs in each case. The first bond hydrolyzed by the HIV-1 protease is the Asn-Tyr linkage in the sequence, -N-I-D-G-D-G-Q-V-N-Y-E-E-, found in the fourth calcium binding loop. In contrast, it is an Ala-Ala bond in the third calcium loop, -D-K-D-G-N-G-Y-I-S-A-A-E-, that is first hydrolyzed by the HIV-2 enzyme, followed in short order by cleavage of the same Asn-Tyr linkage described above. Thereafter, both enzymes proceed to hydrolyze additional peptide bonds, some in common, some not. Considerable evidence exists that inhibitors are bound to the protease in an extended conformation and yet all of the cleavages we observed occur within, or at the beginning of helices in Ca2+/CaM, regions that also appear to be insufficiently exposed for protease binding. Molecular modeling studies indicate that CaM in solution must adopt a conformation in which the first cleavage site observed for each enzyme is unshielded and extended, and that subsequent cleavages involve further unwinding of helices.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- A G Tomasselli
- Biochemistry Unit, Upjohn Company, Kalamazoo, Michigan 49001
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16
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Jarrett HW, Madhavan R. Calmodulin-binding proteins also have a calmodulin-like binding site within their structure. The flip-flop model. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)52443-1] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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17
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A calcium-sensitive fluorescent analog of calmodulin based on a novel calmodulin-binding fluorophore. J Biol Chem 1990. [DOI: 10.1016/s0021-9258(17)30508-2] [Citation(s) in RCA: 31] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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18
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Fluorescent adducts of wheat calmodulin implicate the amino-terminal region in the activation of skeletal muscle myosin light chain kinase. J Biol Chem 1990. [DOI: 10.1016/s0021-9258(18)77183-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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19
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Identification of a region of UDP-galactose:N-acetylglucosamine beta 4-galactosyltransferase involved in UDP-galactose binding by differential labeling. J Biol Chem 1990. [DOI: 10.1016/s0021-9258(18)77282-7] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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20
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Strynadka NC, James MN. Model for the interaction of amphiphilic helices with troponin C and calmodulin. Proteins 1990; 7:234-48. [PMID: 2362945 DOI: 10.1002/prot.340070305] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Crystals of troponin C are stabilized by an intermolecular interaction that involves the packing of helix A from the N-terminal domain of one molecule onto the exposed hydrophobic cleft of the C-terminal domain of a symmetry related molecule. Analysis of this molecular recognition interaction in troponin C suggests a possible mode for the binding of amphiphilic helical molecules to troponin C and to calmodulin. From the template provided by this troponin C packing, it has been possible to build a model of the contact region of mastoporan as it might be bound to the two Ca2+ binding proteins. A possible binding mode of melittin to calmodulin is also proposed. Although some of the characteristics of binding are similar for the two amphiphilic peptides, the increased length of melittin requires a significant bend in the calmodulin central helix similar to that suggested recently for the myosin light chain kinase calmodulin binding peptide (Persechini and Kretsinger: Journal of Cardiovascular Pharmacology 12:501-512, 1988). Not only are the hydrophobic interactions important in this model, but there are several favorable electrostatic interactions that are predicted as a result of the molecular modeling. The regions of troponin-C and calmodulin to which amphiphilic helices bind are similar to the regions to which the neuroleptic drugs such as trifluoperazine have been predicted to bind (Strynadka and James: Proteins 3:1-17, 1988).
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Affiliation(s)
- N C Strynadka
- Department of Biochemistry, University of Alberta, Edmonton, Canada
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21
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Recombinant rat guanidinoacetate methyltransferase: Study of the structure by trace labeling lysine residues with acetic anhydride. ACTA ACUST UNITED AC 1990. [DOI: 10.1016/0020-711x(90)90317-v] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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22
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23
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Chin D, Brew K. Effects of modifying individual amino or carboxyl groups on the affinity of calmodulin for calcineurin. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(19)84837-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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25
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Ovádi J. Effects of drugs on calmodulin-mediated enzymatic actions. PROGRESS IN DRUG RESEARCH. FORTSCHRITTE DER ARZNEIMITTELFORSCHUNG. PROGRES DES RECHERCHES PHARMACEUTIQUES 1989; 33:353-95. [PMID: 2687941 DOI: 10.1007/978-3-0348-9146-2_11] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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26
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Jennett RB, Saffari-Fard A, Sorrell MF, Smith SL, Tuma DJ. Increased covalent binding of acetaldehyde to calmodulin in the presence of calcium. Life Sci 1989; 45:1461-6. [PMID: 2509834 DOI: 10.1016/0024-3205(89)90036-2] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The regulatory protein, calmodulin, undergoes major conformational changes in response to changes in intracellular calcium concentration. Furthermore, calmodulin has been reported to have lysine residues which markedly increase their reactivity toward electrophilic substances in the calcium-loaded state. We found that calmodulin formed two to three times more stable adducts with acetaldehyde in the calcium-loaded state as compared to the calcium-free state. Competition-binding studies showed that calmodulin could preferentially compete with albumin for acetaldehyde in the presence, but not in the absence, of calcium. When calmodulin was in the calcium-loaded state, trifluoperazine, an inhibitor of calmodulin activity, significantly decreased the stable binding of acetaldehyde to the protein, whereas in the calcium-free state, minimal effects on binding were observed. Since calmodulin is involved in regulation of multiple important processes in the cell, it is possible that acetaldehyde-calmodulin adducts could contribute to liver injury by perturbation of calcium-dependent homeostatic mechanisms within the hepatocyte.
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Affiliation(s)
- R B Jennett
- Liver Study Unit, Veterans Administration Medical Center, Omaha, Nebraska
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27
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Kronman MJ. Metal-ion binding and the molecular conformational properties of alpha lactalbumin. Crit Rev Biochem Mol Biol 1989; 24:565-667. [PMID: 2691213 DOI: 10.3109/10409238909080054] [Citation(s) in RCA: 116] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Mammary galactosyltransferase and alpha lactalbumin are the two protein components of lactose synthase which catalyze the transfer of galactose from UDP-gal to glucose in the presence of divalent cations. Recent studies suggest that alpha lactalbumin may have a broader function in modifying cell surface carbohydrates in cell-cell interactions and cell differentiation. Since the discovery that alpha lactalbumin, like galactosyltransferase, is a metalloprotein, there has been a great deal of interest in the metal-binding properties of this protein and how these relate to the metal-ion requirements of the lactose synthase reaction. The recent availability of an X-ray crystal structure of alpha lactalbumin has provided further impetus for establishing the molecular determinants of its biological activity. This review is directed toward critically examining and integrating our present knowledge of the properties of this protein, particularly the relationship between metal-ion binding and conformational state, and how these might relate to its biological function.
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Affiliation(s)
- M J Kronman
- Department of Biochemistry and Molecular Biology, SUNY Health Center, Syracuse
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28
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Wei Q, Jackson AE, Pervaiz S, Carraway KL, Lee EY, Puett D, Brew K. Effects of interaction with calcineurin on the reactivities of calmodulin lysines. J Biol Chem 1988. [DOI: 10.1016/s0021-9258(19)77669-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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29
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Abstract
The crystal structure of mammalian calmodulin has been refined at 2.2 A (1 A = 0.1 nm) resolution using a restrained least-squares method. The final crystallographic R-factor, based on 6685 reflections in the range 2.2 A less than or equal to d less than or equal to 5.0 A with intensities exceeding 2.5 sigma, is 0.175. Bond lengths and bond angles in the molecule have root-mean-square deviations from ideal values of 0.016 A and 1.7 degrees, respectively. The refined model includes residues 5 to 147, four Ca2+ and 69 water molecules per molecule of calmodulin. The electron density for residues 1 to 4 and 148 is poorly defined, and they are not included in the model. The molecule is shaped somewhat like a dumbbell, with an overall length of 65 A; the two lobes are connected by a seven-turn alpha-helix. Prominent secondary structural features include seven alpha-helices, four Ca2+-binding loops, and two short, double-stranded antiparallel beta-sheets between pairs of adjacent Ca2+-binding loops. The four Ca2+-binding domains in calmodulin have a typical EF hand conformation (helix-loop-helix) and are similar to those described in other Ca2+-binding proteins. The X-ray structure determination of calmodulin shows a large hydrophobic cleft in each half of the molecule. These hydrophobic regions probably represent the sites of interaction with many of the pharmacological agents known to bind to calmodulin.
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Affiliation(s)
- Y S Babu
- Department of Pathology, University of Alabama, Birmingham 35294
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30
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Sanyal G, Richard LM, Carraway KL, Puett D. Binding of amphiphilic peptides to a carboxy-terminal tryptic fragment of calmodulin. Biochemistry 1988; 27:6229-36. [PMID: 3219335 DOI: 10.1021/bi00417a006] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Calmodulin (CaM) fragments 1-77 (CaM 1-77) and 78-148 (CaM 78-148) were prepared by tryptic cleavage of CaM. CaM 78-148 exhibited Ca2+-dependent binding to mastoparan X, Polistes mastoparan, and melittin with apparent dissociation constants less than 0.2 microM as judged from changes in the fluorescence spectrum and anisotropy of the single tryptophan residue of each of these cationic, amphiphilic peptides. This interaction was accompanied by a large spectral blue shift of the peptide fluorescence spectrum. These findings are consistent with earlier results [Malencik, D.A., & Anderson, S.R. (1984) Biochemistry 23, 2420-2428] on the binding of mastoparan X to CaM fragment 72-148. The binding of the peptide to CaM 78-148 also caused a significant loss of the accessibility of the peptide tryptophan to the fluorescence quencher acrylamide. The CaM 78-148 induced effects on the fluorescence spectra and tryptophan accessibility of the peptides were most pronounced for mastoparan X, a peptide with tryptophan on the apolar face of the putative amphiphilic helix. The data were comparable with results from parallel experiments on the Ca2+-dependent interaction of these peptides with intact CaM. Difference circular dichroic spectra suggested that binding to CaM 78-148 was associated with the induction of considerable degrees of helicity in the amphiphilic peptides, which by themselves have predominantly random coil structures in aqueous solution. This finding is also reminiscent of the interaction of these peptides with intact CaM.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- G Sanyal
- Department of Chemistry, Hamilton College, Clinton, New York 13323
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31
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32
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Buccigross JM, Nelson DJ. Interactions of spin-labeled calmodulin with trifluoperazine and phosphodiesterase in the presence of Ca(II), Cd(II), La(III), Tb(III), and Lu(III). J Inorg Biochem 1988; 33:139-47. [PMID: 2842452 DOI: 10.1016/0162-0134(88)80042-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Bovine calmodulin analogues, spin-labeled at methionine and tyrosine residues, have been utilized in electron paramagnetic resonance (EPR) studies designed to investigate calmodulin interactions with the antipsychotic drug trifluoperazine and the calmodulin-binding protein 3',5'-cyclic nucleotide phosphodiesterase. Trifluoperazine titrations of spin-labeled calmodulin analogues were carried out in the presence of Ca(II), Cd(II), and Tb(III). Similar experiments were performed with the phosphodiesterase in the presence of Ca(II), Cd(II), La(III), Tb(III), and Lu(III). EPR signals from the methionine-directed probe proved to be more sensitive to the binding of target molecules than signals from the tyrosine-directed probe, perhaps indicating that the spin-labeled methionine is at a site close to the target molecule binding site. While the binding of TFP, as monitored by EPR spectral changes in the methionine spin-labeled calmodulin, was in evidence with Ca(II), Cd(II), and all the lanthanides examined, no binding of phosphodiesterase to calmodulin could be detected in the presence of the lanthanide ions, perhaps due to inactivation of the phosphodiesterase by lanthanide ion binding. The abilities of the spin-labeled calmodulins to activate phosphodiesterase were also investigated. The spin-labeled tyrosine calmodulin was able to activate phosphodiesterase as well as native calmodulin, while a lower degree of activation was found when the spin-labeled methionine analogue was used.
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Affiliation(s)
- J M Buccigross
- Department of Chemistry, College of Mt. St. Joseph, Ohio
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33
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Leung PC, Graves LM, Tipton CL. Characterization of the interaction of ophiobolin A and calmodulin. THE INTERNATIONAL JOURNAL OF BIOCHEMISTRY 1988; 20:1351-9. [PMID: 3243375 DOI: 10.1016/s0020-711x(98)90003-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
1. The fungal toxin ophiobolin A reacts with the epsilon-amino group of lysine to give a conjugated enamine produce with lambda max at 272 nm and a molar extinction of 19,200 per M/cm. 2. Bovine brain calmodulin reacts with ophiobolin A to give a lambda max at 272 nm. 3. One mol of calmodulin reacts with two moles of ophiobolin A. Reaction of 1 mol of ophiobolin A inactivates 1 mol of calmodulin. 4. Ophiobolin A-treated calmodulin is resistant to tryptic cleavage at lysine 77. 5. Ophiobolin A also inhibits Dictyostelium calmodulin which has glutamine instead of lysine at residue 77.
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Affiliation(s)
- P C Leung
- Department of Molecular Biology, Research Institute of Scripps Clinic, La Jolla, CA 92037
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34
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Strynadka NC, James MN. Two trifluoperazine-binding sites on calmodulin predicted from comparative molecular modeling with troponin-C. Proteins 1988; 3:1-17. [PMID: 3375233 DOI: 10.1002/prot.340030102] [Citation(s) in RCA: 72] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Among the known regulatory proteins that are conformationally sensitive to the binding of calcium ions, calmodulin and troponin-C have the greatest primary sequence homology. This observation has led to the conclusion that the most accurate predicted molecular model of calmodulin would be based on the X-ray crystallographic coordinates of the highly refined structure of turkey skeletal troponin-C. This paper describes the structure of calmodulin built from such a premise. The resulting molecular model was subjected to conjugate gradient energy minimization to remove unacceptable intramolecular non-bonded contacts. In the analysis of the resulting structure, many features of calmodulin, including the detailed conformation of the Ca2+-binding loops, the amino- and carboxy-terminal hydrophobic patches of the Ca2+-bound form, and the several clusters of acidic residues can be reconciled with much of the previously published solution data. Calmodulin is missing the N-terminal helix characteristic of troponin-C. The deletion of three residues from the central helical linker (denoted D/E in troponin-C) shortens the molecule and changes the orientation of the two domains of calmodulin by 60 degrees relative to those in troponin-C. The molecular model has been used to derive two possible binding sites for the antipsychotic drug trifluoperazine, a potent competitive inhibitor of calmodulin activity.
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Affiliation(s)
- N C Strynadka
- Medical Research Council of Canada Group in Protein Structure and Function, Department of Biochemistry, University of Alberta, Edmonton
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35
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Guerini D, Krebs J, Carafoli E. Stimulation of the erythrocyte Ca2+-ATPase and of bovine brain cyclic nucleotide phosphodiesterase by chemically modified calmodulin. EUROPEAN JOURNAL OF BIOCHEMISTRY 1987; 170:35-42. [PMID: 2826158 DOI: 10.1111/j.1432-1033.1987.tb13664.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Chemically modified calmodulins have been used to investigate structural features which are important for the interaction of the activator with targets. Carbamoylation of lysine residues had no influence on the ability of calmodulin to stimulate the plasma membrane Ca2+-ATPase whereas the stimulation of the bovine brain cyclic-nucleotide phosphodiesterase was reduced up to 50%. Different species of carbamoylated calmodulin have been isolated but no differences were detected in their interaction with the cyclic-nucleotide phosphodiesterase. Modification of arginine residues by 1,2-cyclohexanedione had no effect of the stimulation of the phosphodiesterase but reduced by 40% the stimulation of the erythrocyte Ca2+ ATPase. Mild oxidation of methionines by N-chlorosuccinimide produced a number of differently modified calmodulins. The different species have been purified and the modified residues have been identified. They affected the two different test enzymes to different extents indicating that methionines in the central helix of calmodulin are of greater importance for the interaction with the phosphodiesterase, whereas methionines located in the C-terminal half of calmodulin are more important for the interaction with the Ca2+-ATPase.
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Affiliation(s)
- D Guerini
- Laboratory of Biochemistry, Swiss Federal Institute of Technology, Zürich
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36
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Jackson AE, Harris TM, Puett D. Characterization of specific fluorenylmethyloxycarbonyl-containing calmodulin adducts by spectroscopy and phosphodiesterase stimulation. Protein J 1987. [DOI: 10.1007/bf00276736] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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37
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38
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Manalan AS, Klee CB. Affinity selection of chemically modified proteins: role of lysyl residues in the binding of calmodulin to calcineurin. Biochemistry 1987; 26:1382-90. [PMID: 3105580 DOI: 10.1021/bi00379a026] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
In affinity selection, calcineurin selects from a population of randomly modified calmodulins those species with which it prefers to interact. The method shows that acetylation of lysines affects calmodulin so as to interfere with its ability to interact with calcineurin. Monoacetylation of any lysine of calmodulin reduces its affinity for calcineurin by 5-10-fold. Multiple acetylations amplify the loss of affinity; none of the modifications are imcompatible with activity. The lack of selectivity of calcineurin against any particular modified lysine indicates that the loss of affinity reflects changes induced by the removal of the charged groups and suggests an important role for electrostatic interactions in the cooperative structural transitions which calmodulin undergoes upon binding its target proteins or calcium. In the presence of calcineurin, a large and specific decrease in the rate of acetylation of Lys-75 and -148 of calmodulin is observed. The reactivity of the same residues is greatly increased in the presence of calcium alone [Giedroc, D. P., Sinha, S. K., Brew, K., & Puett, D. (1985) J. Biol. Chem. 260, 13406-13413]. Lys-75, located in the central helix, and the C-terminal Lys-148 [Babu, Y. S., Sacks, J. S., Greenhouse, T. J., Bugg, C. E., Means, A. R., & Cook, W. J. (1985) Nature (London) 315, 37-40] may act as sensors of the calmodulin allosteric transitions. Their reactivity changes in opposite directions in response to calcium-induced or calcineurin-induced structural changes. The reactivity of other residues such as Lys-21, decreased in the presence of calcineurin but not calcium, is also affected by a conformational change which is induced specifically by calcineurin.
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39
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40
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Faust F, Slisz M, Jarrett H. Calmodulin is labeled at lysine 148 by a chemically reactive phenothiazine. J Biol Chem 1987. [DOI: 10.1016/s0021-9258(18)61599-6] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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41
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Jackson AE, Carraway KL, Payne ME, Means AR, Puett D, Brew K. Association of calmodulin and smooth muscle myosin light chain kinase: application of a label selection technique with trace acetylated calmodulin. Proteins 1987; 2:202-9. [PMID: 3128785 DOI: 10.1002/prot.340020305] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
A method is described for rapidly surveying the effects of modifying individual amino acid residues of a protein on its ability to interact specifically with another macromolecule. The procedure has been used to examine the individual roles of the seven lysyl residues of calmodulin in its ability to bind to smooth muscle myosin light chain kinase; previous studies by Jackson et al. (J. Biol. Chem. 261:1226-12232, 1986) have suggested that certain lysines may be located close to the interaction site. Trace [3H]-acetylated calmodulin, consisting predominantly of molecules acetylated at single sites together with unmodified protein, was incubated in excess (five- to 20-fold) with smooth muscle MLC kinase to allow the modified and unmodified molecules to compete for binding to the enzyme. Subsequently, the calmodulin-enzyme complex was separated from unbound calmodulin, and the level of acetylation of each of the seven lysines of the bound fraction of calmodulin was determined and compared to that of each corresponding group of the starting preparation. Significant changes were found at only two of the lysines, 21 and 75, where the extent of acetylation in the bound fraction was three- and fivefold lower, respectively, than that in the original preparation. These results were reproducible in three separate selection experiments employing both chicken and turkey gizzard MLC kinase. It is concluded that acetylation of calmodulin at either lysine 21 or 75 markedly reduces its affinity for MLC kinase, but acetylation at any of the other lysines (13, 30, 77, 94, or 148) has only minor effects.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- A E Jackson
- Department of Biochemistry, University of Miami School of Medicine, Florida 33101
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42
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43
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Tertrin-Clary C, Chenut MC, de la Llosa P. Activation of a cyclic nucleotide phosphodiesterase and of a protein kinase by chemically modified calmodulin. THE INTERNATIONAL JOURNAL OF BIOCHEMISTRY 1987; 19:949-55. [PMID: 2822504 DOI: 10.1016/0020-711x(87)90177-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
1. Several calmodulin derivatives prepared by chemical modification of lysine residues were tested using bovine heart cyclic nucleotide phosphodiesterase and wheat germ calmodulin-dependent protein kinase. 2. The effect of chemical modification on the activation capacity of calmodulin for the two studied enzymes was different. 3. This was particularly noticeable in the case of alkylated derivatives which exhibited a higher affinity than native calmodulin towards phosphodiesterase but a lower affinity towards protein kinase. 4. The efficiency of these derivatives (maximal activation) was higher than that of native calmodulin in relation with the protein kinase.
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44
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Abstract
The differential reactivities of individual lysines on porcine testicular calmodulin were determined by trace labeling with high specific activity [3H]acetic anhydride as a function of the molar ratio of Ca2+ to calmodulin. In progressing from the Ca2+-depleted form of the protein to a Ca2+:calmodulin molar ratio of 5:1, six of the seven lysyl residues exhibited a modest 1.5- to 3.0-fold increase in reactivity. Lys 75, in contrast, was enhanced in reactivity greater than 20-fold. When the change in reactivity of each lysine was normalized as a percentage of the maximum change, most of the residues were found to fall into two distinct classes. One class, comprising lysines 94 and 148 from the two carboxy terminal Ca2+-binding domains 3 and 4, respectively, exhibited about 90% of their reactivity change when the Ca2+:calmodulin molar ratio was 2:1, and these residues were perturbed very little upon further addition of Ca2+. The other class, encompassing lysines 13, 21, and 30 from the amino terminal domain 1 and Lys 75 from the extended helix connecting the two globular lobes of calmodulin, underwent most of their overall reactivity change (55-70%) between 2 and 5 equivalents of Ca2+ per mol of calmodulin. Lys 77 was distinct in its pattern of change, undergoing approximately equal changes with each Ca2+ increment. These results are consistent with a model where Ca2+ first binds to the two carboxy terminal sites of calmodulin with no apparent preference, concomitant with minor alterations in the microenvironments of lysines in the unoccupied amino terminal domains. The third and fourth Ca2+ ions then bind to these latter two domains, again with no evidence of preference, with little change in the lysine reactivities at the carboxy terminus of the molecule. The environments of groups in the central helix appear to undergo changes in a manner that reflects their proximity to the amino and carboxy terminal domains. In the course of this work, it was found that Lys 94 in apocalmodulin is specifically perturbed by the addition of EGTA, suggesting that the chelating agent may interact with calmodulin at or near the third Ca2+-binding domain.
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45
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Erickson-Viitanen S, DeGrado WF. Recognition and characterization of calmodulin-binding sequences in peptides and proteins. Methods Enzymol 1987; 139:455-78. [PMID: 3587035 DOI: 10.1016/0076-6879(87)39106-2] [Citation(s) in RCA: 128] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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46
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Jackson AE, Puett D. Binding of trifluoperazine and fluorene-containing compounds to calmodulin and adducts. Biochem Pharmacol 1986; 35:4395-400. [PMID: 3790160 DOI: 10.1016/0006-2952(86)90754-9] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Calmodulin can be specifically acylated with a fluorene-containing hydrophobic spin-labeling reagent at just Lys 75 or at Lys 75 and Lys 148. The binding of trifluoperazine to calmodulin and the two adducts was determined using a Hummel-Dreyer procedure, and binding of the phenothiazine was found to be characterized by apparent positive cooperativity and an apparent limiting stoichiometry of about seven binding sites per protein molecule. Two non-reactive fluorene-containing compounds were synthesized, and both reagents exhibited far less binding to calmodulin than did trifluoperazine. One of these was also assayed for binding to the monolabeled adduct, and this binding was about half that observed with calmodulin and was non-cooperative. Thus, the qualitative and quantitative binding parameters of hydrophobic groups to calmodulin can be quite different.
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47
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Effects of the binding of myosin light chain kinase on the reactivities of calmodulin lysines. J Biol Chem 1986. [DOI: 10.1016/s0021-9258(18)67228-x] [Citation(s) in RCA: 33] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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48
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Linse S, Drakenberg T, Forsén S. Mastoparan binding induces a structural change affecting both the N-terminal and C-terminal domains of calmodulin. A 113Cd-NMR study. FEBS Lett 1986; 199:28-32. [PMID: 3956744 DOI: 10.1016/0014-5793(86)81217-0] [Citation(s) in RCA: 33] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
113Cd-NMR studies of solutions of cadmium-loaded calmodulin (Cd4CaM) and the tetradecapeptide mastoparan in different ratios show that mastoparan binds to Cd4CaM with high affinity. The off-rate of protein- bound mastoparan is found to be 40 s-1 or less. The binding of one molecule of mastoparan to Cd4CaM is observed to affect all four metal-binding sites, indicating that both the N-terminal and C-terminal globular domains of the protein undergo conformational changes.
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49
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Abstract
Studies utilizing the interaction of melittin with the 1-106 fragment of calmodulin, the protection of calmodulin from tryptic digestion by melittin, and the interaction of the carbocyanine dye Stains-all with the calmodulin-melittin complex have indicated that complex formation of calmodulin with melittin involves the alpha-helical connecting bridge joining the N- and C-terminal lobes of calmodulin.
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