SEARCH · PubMed Health

Results for “Calmodulin”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,369 records · Page 76Linked to original sources

PubMed1981

Interaction of calmodulin with myosin light chain kinase and cAMP-dependent protein kinase in bovine brain.

Myosin light chain kinase and a fraction of type II cAMP-dependent protein kinase have been partially purified from bovine brain by affinity chromatography on calmodulin-Sepharose. The myosin kinase was purified approximately 3700-fold and has an estimated molecular weight of 130,000 +/- 10,000 by sodium dodecyl sulfate gel electrophoresis. A fraction of soluble cAMP-dependent protein kinase also bound to calmodulin-Sepharose and was purified 2300-fold. A fraction of this cAMP-dependent protein kinase after purification by glycerol gradient centrifugation was shown to contain the two subunits of calcineurin, a major calmodulin-binding protein in brain, and the two subunits of type II cAMP-dependent protein kinase in a ratio of 1:1:2:2. Its sedimentation coefficient was 8.1 S and 9.0 S when centrifuged in the absence or presence of calmodulin, suggesting the formation of a complex between calmodulin and protein kinase. Our results suggest the possibility that calcineurin may be involved in the interaction between the protein kinase and calmodulin. Furthermore, our studies imply that the regulatory subunit of the cAMP-dependent protein kinase, but not the catalytic subunit, is the site of interaction with calmodulin since the catalytic subunit of protein kinase was partially resolved from the complex by cAMP.

Animals↗

PubMed1983

[Effect of lipids on the binding of calmodulin with cyclic nucleotide phosphodiesterase].

The effects of various lipids on calmodulin interaction with Ca-dependent phosphodiesterase were investigated. Palmitic, myristic and stearic acids increased the enzyme activity; the degree of the enzyme activation by calmodulin was decreased thereby. Oleic acid produced a weak activating effect on phosphodiesterase but completely blocked calmodulin action. The effects of the fatty acids under study were reversible, the activation constant was equal to 10(-4)-5 X 10(-4) M. In the presence of Ca2+ phosphoinositides and fatty acids changed the fluorescence intensity of dansyl-labelled calmodulin; in the absence of Ca2+ the lipids did not affect protein fluorescence. The lipids had no influence on the protein affinity for Ca2+. During chromatography of phosphodiesterase on calmodulin-Sepharose the enzyme was eluted from the column both in the presence of EGTA and palmitic acid. It was concluded that fatty acids prevent the formation of the calmodulin - phosphodiesterase complex. This effects may both be due to the lipid binding to the enzyme and to calmodulin.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMed1984

Effects of metal cations and calmodulin antagonists on [3H] nitrendipine binding in smooth and cardiac muscle.

It was previously reported that [3H]nitrendipine binding to a microsomal fraction from intestinal smooth muscle was dependent upon the presence of divalent metal cations (Bolger et al., J. Pharmacol. Exp. Ther. 225: 291-309, 1983). The effects of cations and calmodulin antagonists on [3H]nitrendipine binding in smooth and cardiac muscle have been studied further. Treatment of ileal and aortic smooth muscle and cardiac muscle with EDTA reduced specific [3H]nitrendipine binding by 70 to 95%. Microsomes from rabbit ventricle were more resistant to EDTA treatment than were those from ileal smooth muscle, but low concentrations of Ca++ (less than 10(-5) M) produced half-maximal restoration of binding in both tissues. The ability of cations at a concentration of 10(-3) M to restore binding to membranes from guinea-pig ileum was in the sequence, Ca++ = Sr++ greater than Mg++ = Mn++ = Co++ greater than Ba++ = Ni++ greater than Zn++ = Cd++ greater than La = Sm = Tm . In contrast to the activation of calmodulin-dependent processes, the ability of these cations to restore [3H]nitrendipine binding did not correlate linearly with ionic radius. However, calmodulin antagonists were found to inhibit [3H]nitrendipine binding with the order of potency: pimozide greater than less than calmidazolium (R 24571) greater than trifluoperazine greater than chlorpromazine greater than promethazine greater than chlorpromazine sulfoxide, that correlates quite well with the potency of these drugs as inhibitors of calmodulin-dependent processes. The results suggest that calmodulin antagonists bind to a protein associated with the [3H]nitrendipine binding site that has a hydrophobic domain similar to that exposed on calmodulin by Ca++, but that this protein is not calmodulin itself.

Animals↗

PubMed1981

The Ca2+-pumping ATPase of heart sarcolemma. Characterization, calmodulin dependence, and partial purification.

The (Ca2+ + Mg2+) ATPase of dog heart sarcolemma (Caroni, P., and Carafoli, E. (1980) Nature 283, 765-767) has been characterized. The enzyme possesses an apparent Km (Ca2+) of 0.3 +/- 02 microM, a Vmax of Ca2+ transport of 31 nmol of Ca2+/mg of protein/min, and an apparent Km (ATP) of 30 microM. It is only slightly influenced by monovalent cations and is highly sensitive to orthovanadate (Ki = 0.5 +/- 0.1 microM). The high vanadate sensitivity has been used to distinguish the sarcolemmal and the contaminating sarcoplasmic reticulum Ca2+-dependent ATPase in heart microsomal fractions. Calmodulin has been shown to be present in heart sarcolemma. Its depletion results in the transition of the Ca2+-pumping ATPase to a low Ca2+ affinity; readdition of calmodulin reverses this effect. The Na+/Ca2+ exchange system was not affected by calmodulin. The results of calmodulin extraction can be duplicated by using the calmodulin antagonist trifluoperazine. The calmodulin-depleted Ca2+-ATPase has been solubilized from the sarcolemmal membrane and "purified" on a calmodulin affinity chromatography column. One major (Mr = 150,000) and 3 minor protein bands could be eluted from the column with ethylene glycol bis(beta-aminoethyl ether)N,N,N',N'-tetraacetic acid (EGTA). The major protein band (72%) has Ca2+-dependent ATPase activity and can be phosphorylated by [gamma]32P]ATP in a Ca2+-dependent reaction.

Animals↗

PubMed1983

[Effect of fatty acids on calmodulin regulation of adenylate cyclase from the brain striatal system].

p3eincubation of striatal membranes for 1 hour at 37 degrees C in the presence of calmodulin results in thermal inactivation of the calmodulin-insensitive adenylate cyclase; the activity of the calmodulin-sensitive form of the enzyme remains practically unchanged. Using a membrane preparation of striatal adenylate cyclase possessing a high sensitivity to calmodulin, the effects of fatty acids on regulation of adenylate cyclase by Ca2+ and calmodulin were studied. It was found that linolenic and palmitic acids exert a weak activating effect on adenylate cyclase in the presence of Ca2+, but do not practically affect the enzyme in Ca2+ free media. Linolenic acid almost completely inhibits the activation of adenylate cyclase by calmodulin; palmitic acid has no such effect. It was assumed that unsaturated fatty acids may prevent the interaction of adenylate cyclase with calmodulin.

Adenylyl Cyclases↗

PubMed1982

A calmodulin-dependent protein kinase system from skeletal muscle sarcoplasmic reticulum. Phosphorylation of a 60,000-dalton protein.

The calmodulin plus Ca2+-dependent phosphorylation of a 60,000-dalton protein was detectable in muscle homogenates and in purified sarcoplasmic reticulum membranes. Phosphorylation was enhanced when purified sarcoplasmic reticulum vesicles were extracted with 1 mM ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid at pH 8.0 to remove endogenous calmodulin and lower the level of residual phosphorylation. Phosphorylation of the 60,000-dalton protein was stimulated by NaF, reached maximal levels of about 55 pmol/mg of protein within 90 s and was not affected by cAMP. Half-maximal stimulation of phosphorylation required 0.1 microM calmodulin and maximal phosphorylation required 0.6 microM calmodulin; in the presence of 0.6 microM calmodulin, maximal phosphorylation required 0.3 microM Ca2+. Calmodulin-dependent phosphorylation of the 60,000-dalton protein was inhibited by trifluoperazine with a Ki of 5 microM. The pH optimum of phosphorylation was below 6.0 and was inhibited over 90% at pH 8.0. The purified 60,000-dalton protein contained phosphoserine and phosphothreonine but no phosphotyrosine. Two-dimensional gel electrophoresis and immunoprecipitation showed that the 60,000-dalton phosphoprotein was not calsequestrin. Endo-beta-N-acetylglucosaminidases H and D digestion failed to alter its molecular weight, indicating that it was not a glycoprotein. A functional role for the phosphorylation system is suggested by the observations that ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid extraction, which removes endogenous calmodulin and lowers endogenous phosphorylation levels, and high pH, which inhibits phosphorylation, lead to greatly diminished Ca2+ accumulation by sarcoplasmic reticulum vesicles.

Animals↗

PubMed1982

Two types of calcium-dependent protein phosphorylations modulated by calmodulin antagonists. Naphthalenesulfonamide derivatives.

Ca2-dependent protein phosphorylations activated by calmodulin or phospholipid were studied using selective inhibitors. Both protein phosphorylations were inhibited by N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7) and its derivatives. Kinetic analysis indicated that the primary effect of these agents was mediated through a competitive inhibition of enzyme activation by interaction with calmodulin or phospholipid, and Ki values of W-7 for calmodulin-dependent phosphorylation and phospholipid-dependent protein kinase were 12 microM and 110 microM, respectively. The addition of Ca2+ inhibited the binding of [3H]W-7 to phosphatidylserine but not the binding to calmodulin. The potencies of naphthalenesulfonamide derivatives as derivatives as inhibitors of Ca2+, calmodulin-dependent protein kinase were dependent on the length of the alkyl chain (C2-C10) but not on Ca2+-activated, phospholipid-dependent protein kinase. These results suggest that naphthalenesulfonamide derivatives may be more selective inhibitors of Ca2+, calmodulin-dependent protein phosphorylation than is Ca2+-activated, phospholipid-dependent protein kinase and that the mechanism of interaction between W-7 and phosphatidylserine differs from the interaction between W-7 and calmodulin. These agents are useful tools for elucidating the physiological role of Ca2+-dependent protein phosphorylation.

Calcium↗

PubMed1982

Positive correlation between calmodulin content and hepatoma growth rates.

Calmodulin contents of normal rat liver, host liver [bearing hepatoma 5123t.c.(h)], regenerating liver, and Morris hepatomas 7800, 5123t.c.(h), and 7794A were determined by phosphodiesterase assay and by radioimmunoassay. The calmodulin levels determined by both assays were significantly increased in three hepatomas when compared to the corresponding values of normal liver. The order of increase in calmodulin content was as follows: normal liver = host liver less than 7794A (slow growth rate) less than 5123t.c.(h) (intermediate growth rate) less than 7800 (fast growth rate). In regenerating liver (24 hr after partial hepatectomy), the calmodulin content was not different from that of normal liver. In good agreement with the literature, the calmodulin values measured by the phosphodiesterase assay were always lower than those determined by radioimmunoassay. Calcium and magnesium contents were measured by atomic absorption spectrophotometry in acid digests of these tissues. Both cation contents were significantly increased in the three hepatomas studied when compared to the corresponding values of normal liver; the extent of increase for calcium content (120 to 240%) was much greater than that for magnesium (30 to 40%). The order of increase for both cations was as follows: normal liver = host liver less than 5123t.c.(h) less than 7794A less than 7800. Therefore, there does not appear to be any correlation between the cation contents and hepatoma growth rates. In regenerating liver, magnesium content was about 14% higher than that of normal liver. In summary, the results indicate that only the increase of calmodulin appears to correlate positively with the growth rate of these tumors. This correlation suggests that calmodulin may be involved in tumor cell growth regulation.

Animals↗

PubMed1994

L-arginine and calmodulin regulation of the heme iron reactivity in neuronal nitric oxide synthase.

Neuronal nitric oxide synthase (NOS) is a calmodulin-dependent, flavin-containing hemoprotein that forms NO from L-arginine, NADPH, and molecular oxygen. Calmodulin binding to NOS triggers reduction of its heme groups (Abu-Soud, H., and Stuehr, D.J. (1993) Proc. Natl. Acad. Sci. U.S.A. 90, 10769-10762), leading to NADPH oxidation and NO synthesis. We have examined how L-arginine and calmodulin control the ligand binding and electron acceptor properties of the NOS heme iron. In the absence of bound calmodulin, ferric NOS exhibited a Kd of 0.6 microM for L-arginine, as determined by the substrate-dependent shift in heme spin equilibrium toward a high spin state. L-Arginine binding reduced the affinity of the ferric NOS heme for cyanide by 8-fold. Carbon monoxide binding to substrate-free ferrous NOS occurred at a rate of 2 x 10(5) M-1 S-1; this rate was decreased 12-fold when L-arginine was bound. In contrast, bound calmodulin did not significantly affect cyanide or carbon monoxide binding to the NOS heme, nor did it alter NOS binding affinity for L-arginine. Anaerobic titration of a calmodulin-bound, L-arginine-free NOS with NADPH led to incomplete reduction of the heme iron; full reduction was achieved only in the presence of added L-arginine. Thus, our data suggest that L-arginine controls NOS heme iron reactivity in at least two ways: 1) it slows ligand interactions by binding in the distal pocket very near the heme and 2) it also appears to increase the reduction potential of the iron. In contrast, bound calmodulin does not alter the NOS affinity for L-arginine or heme ligands and may function solely as a switch that enables electrons to pass from the flavin domain onto the heme iron.

Amino Acid Oxidoreductases↗

PubMed1994

Characterization of trimethyllysine 115 in calmodulin by 14N and 13C NMR spectroscopy.

In this paper, we describe three approaches to study the single trimethyllysine 115 in calmodulin. First, 14N NMR spectroscopy has been used as a novel spectroscopic tool. Because of the unique symmetrical tetrahedral substitution of its side chain, the trimethyllysine residue gives rise to a sharp 14N NMR resonance; hence, this has allowed the detection and quantitation of the level of trimethylation. Trimethyllysine side chains of bovine testis calmodulin and yeast cytochrome c were shown to have a high mobility in aqueous solution as determined by 14N NMR relaxation measurements. Second, we have purified mammalian calmodulin from an overproducing Escherichia coli strain. By comparison of the 1H-13C heteronuclear multiple quantum coherence spectra of 13C-dimethylated calmodulin samples from bovine testis and E. coli, the resonance for Lys-115 in bacterially expressed calmodulin could be identified. pH titration experiments showed that epsilon-NH2 group of Lys-115 has a normal pKa value both in the apo and Ca2+ forms of the protein and in a complex of calmodulin with a 22-residue calmodulin-binding peptide derived from myosin light chain kinase. Third, we have shown that mutation of Lys-115 to the uncharged Gln residue does not alter the ability of the protein to stimulate the enzymes cyclic nucleotide phosphodiesterase and myosin light chain kinase. These results show that the trimethylation of Lys-115 is not caused by an unusual pKa and reactivity of its epsilon-NH2 group and that its side chain remains flexible. Moreover, our data suggest that the introduction of a permanent positive charge on Lys-115 by trimethylation is also not the major reason for this specific post-translational modification.

Amino Acid Sequence↗

PubMed1993

Structure and organization of a novel calmodulin gene of Arabidopsis thaliana.

The calcium binding protein calmodulin is involved in regulating various cellular and biochemical processes. A gene for calmodulin has been isolated from a genomic library of Arabidopsis thaliana constructed in lambda EMBL-4 using a heterologous cDNA probe from electric eel. The genomic clone was found to contain a complete copy of a distinct calmodulin (CaM) gene. A comparison of the nucleotide sequence with those from the other plant and animal systems reveals that the Arabidopsis CaM gene contains two exons and a single intron of 364 bp. The intron splits the triplet encoding the 25th amino acid of the protein. The Arabidopsis calmodulin protein appears to be distinct in containing a single amino acid substitution, arg to lys at the 126th position from the other known plant and animal calmodulins. The 5'-upstream region of this CaM gene (ACaM4) contains several known sequence-elements, a few of which are known to be implicated in transcriptional activation in response to light, U.V. radiation and heat shock besides the presence of many small multiple repeats. The Southern hybridization analysis and a comparison of nucleotide sequence with those of the other calmodulin genes of Arabidopsis indicate that the calmodulin gene, ACaM4, belongs to a small multigene family consisting of at least four members in the Arabidopsis genome.

Amino Acid Sequence↗

PubMed1993

Purification and properties of calmodulin from Phymatotrichum omnivorum.

Mycelia of Phymatotrichum omnivorum obtained at 10 day intervals during 10 to 50 days of growth were used for isolating calmodulin, and studying its effect on glycogen synthase, phosphorylase, phosphorylase kinase, cyclic AMP phosphodiesterase and Ca++ATPase. Glycogen synthase was inhibited until the 30th day by calmodulin, whereas calmodulin obtained from the 40th day stimulated glycogen synthase activity and the 50th day sample had no effect. cAMP phosphodiesterase and Ca++ATPase of P. omnivorum were stimulated by the respective calmodulin. Molecular weight of the purified fungal calmodulin was approximately 18 kD as revealed by sodium dodecyl sulphate gel electrophoresis. Trifluoperazine, dibucaine and lidocaine inhibited calmodulin activity and calmodulin activation of PDE, respectively.

Calcium-Transporting ATPases↗

PubMed1996

Modulation of the cGMP-activated conductance of the plasma membrane of photoreceptor cells by calmodulin.

The effect of calmodulin on the integral cGMP-activated conductance of ROS plasma membrane has been investigated by using the "patch-clamp" techniques (inside-out configuration). Calmodulin increased the apparent Michaelis constant (Km) from 19 +/- 1.5 (in the absence of calmodulin) to 33.7 +/- 5.5 mM. However, it did not influence the Hill coefficient and the maximum conductance of cGMP-channels. Ca2+ ions were required for the calmodulin effect (EC(50)= 452 +/- 47 nM). The results of our experiments with the use of 8-Br-cGMP and IBMX suggest that the modulating action of calmodulin was not mediated by the ROS phosphodiesterase activation. The action of some calmodulin inhibitors has been tested. On the basis of our study calmodulin is suggested to be very significant for the recovery and light adaptation processes by changing the affinity of the cGMP-channel for agonist.

Animals↗

PubMed1999

Interactions of calmodulin and alpha-actinin with the NR1 subunit modulate Ca2+-dependent inactivation of NMDA receptors.

Glutamate receptors are associated with various regulatory and cytoskeletal proteins. However, an understanding of the functional significance of these interactions is still rudimentary. Studies in hippocampal neurons suggest that such interactions may be involved in calcium-induced reduction in the open probability of NMDA receptors (inactivation). Thus we examined the role of the intracellular domains of the NR1 subunit and two of its binding partners, calmodulin and alpha-actinin, on this process using NR1/NR2A heteromers expressed in human embryonic kidney (HEK) 293 cells. The presence of the first 30 residues of the intracellular C terminus of NR1 (C0 domain) was required for inactivation. Mutations in the last five residues of C0 reduced inactivation and produced parallel shifts in binding of alpha-actinin and Ca2+/calmodulin to the respective C0-derived peptides. Although calmodulin reduced channel activity in excised patches, calmodulin inhibitors did not block inactivation in whole-cell recording, suggesting that inactivation in the intact cell is more complex than binding of calmodulin to C0. Overexpression of putative Ca2+-insensitive, but not Ca2+-sensitive, forms of alpha-actinin reduced inactivation, an effect that was overcome by inclusion of calmodulin in the whole-cell pipette. The C0 domain also directly affects channel gating because NR1 subunits with truncated C0 domains that lacked calmodulin or alpha-actinin binding sites had a low open probability. We propose that inactivation can occur after C0 dissociates from alpha-actinin by two distinct but converging calcium-dependent processes: competitive displacement of alpha-actinin by calmodulin and reduction in the affinity of alpha-actinin for C0 after binding of calcium to alpha-actinin.

Actinin↗

PubMed1999

Increased cytosolic Ca(2+) concentration in endothelial cells by calmodulin antagonists.

Many functions of endothelial cells are Ca(2+)/calmodulin dependent, whereas the role of calmodulin in the regulation of cytosolic Ca(2+) ([Ca(2+)](i)) remains largely unexplained. In the present study, effects of various calmodulin antagonists on [Ca(2+)](i) were investigated in cultured aortic endothelial cells loaded with the Ca(2+)-sensitive dye fura-2/AM, and were compared with those of calmodulin-dependent protein kinase II (CaM kinase II) inhibitors. The calmodulin antagonists W-7, calmidazolium and fendiline provoked dose-dependent increases in [Ca(2+)](i). However, the CaM kinase II inhibitors KN-93 and lavendustin C had no effect on [Ca(2+)](i). In the absence of extracellular Ca(2+), pretreatment of cells with bradykinin (BK) and thapsigargin completely prevented W-7-stimulated increase in [Ca(2+)](i). Alternatively, pretreatment with W-7 also completely blocked BK- and thapsigargin-stimulated increases in [Ca(2+)](i). The time course of the Ca(2+)-response in W-7 treated cells was identical to that in thapsigargin-treated cells, but not that in BK-stimulated cells, suggesting that calmodulin antagonists could share a common signaling pathway with thapsigargin to increase [Ca(2+)](i) in endothelial cells. These findings indicate that calmodulin is involved in the regulation of [Ca(2+)](i), and may play an important role in the uptake of Ca(2+) to intracellular stores.

Animals↗

PubMed1994

Calmodulin and the regulation of smooth muscle contraction.

Calmodulin, the ubiquitous and multifunctional Ca(2+)-binding protein, mediates many of the regulatory effects of Ca2+, including the contractile state of smooth muscle. The principal function of calmodulin in smooth muscle is to activate crossbridge cycling and the development of force in response to a [Ca2+]i transient via the activation of myosin light-chain kinase and phosphorylation of myosin. A distinct calmodulin-dependent kinase, Ca2+/calmodulin-dependent protein kinase II, has been implicated in modulation of smooth-muscle contraction. This kinase phosphorylates myosin light-chain kinase, resulting in an increase in the calmodulin concentration required for half-maximal activation of myosin light-chain kinase, and may account for desensitization of the contractile response to Ca2+. In addition, the thin filament-associated proteins, caldesmon and calponin, which inhibit the actin-activated MgATPase activity of smooth-muscle myosin (the cross-bridge cycling rate), appear to be regulated by calmodulin, either by the direct binding of Ca2+/calmodulin or indirectly by phosphorylation catalysed by Ca2+/calmodulin-dependent protein kinase II. Another level at which calmodulin can regulate smooth-muscle contraction involves proteins which control the movement of Ca2+ across the sarcolemmal and sarcoplasmic reticulum membranes and which are regulated by Ca2+/calmodulin, e.g. the sarcolemmal Ca2+ pump and the ryanodine receptor/Ca2+ release channel, and other proteins which indirectly regulate [Ca2+]i via cyclic nucleotide synthesis and breakdown, e.g. NO synthase and cyclic nucleotide phosphodiesterase. The interplay of such regulatory mechanisms provides the flexibility and adaptability required for the normal functioning of smooth-muscle tissues.

Amino Acid Sequence↗

PubMed1991

Concerted regulation of protein phosphorylation and dephosphorylation by calmodulin.

The multiple functions of calmodulin in brain bring to light an apparent paradox in the mechanism of action of this multifunctional regulatory protein: How can the simultaneous calmodulin stimulation of enzymes with opposing functions, such as cyclic nucleotide phosphodiesterases and adenylate cyclase, which are responsible for the degradation and synthesis of cAMP, respectively, be physiologically significant? The same question applies to the simultaneous activation of protein kinases (in particular calmodulin kinase II) and a protein phosphatase (calcineurin). One could propose that the protein kinase(s) and the phosphatase may be located in different cells or in different cellular compartments, and are therefore not antagonizing each other. The same result could be achieved if the specific substrates of these enzymes have different cellular localizations. This does not seem to be the case. In many areas of the brain the two enzymes and their substrates coexist in the same cell. For example, the hippocampus is rich in calmodulin kinase II, calcineurin and substrates for the two enzymes. A more general scheme is presented here, based on different mechanisms of the calmodulin regulation of the two classes of enzyme, which helps to solve this apparent inconsistency in the mechanism of action of calmodulin.

Animals↗

PubMed1988

Identification of the multifunctional calmodulin-dependent protein kinase in the cytosol, sarcoplasmic reticulum, and sarcolemma of rabbit skeletal muscle.

A multifunctional calmodulin-dependent protein kinase (calmodulin kinase) was purified from the cytosol of rabbit skeletal muscle as a subunit of 58 kDa. A 58-kDa protein in sarcoplasmic reticulum (SR) and sarcolemma (SL) of rabbit skeletal muscle was endogenously phosphorylated in a calmodulin-dependent manner. The 58-kDa protein in SR and SL was considered to be identical to the subunit of cytosol calmodulin kinase on the basis of immunoreactivity, calmodulin binding, and autophosphorylation studies and on the patterns of protease-treated phosphopeptides. Calmodulin kinase showed broad substrate specificity and phosphorylated troponins I and T.

Animals↗