Heterogeneity of smooth muscle myosin light chain kinase. Characterization of isoelectric variants.
Purified chicken gizzard myosin light chain kinase (MLCK) analyzed by anion-exchange high-performance liquid chromatography (HPLC) can be consistently resolved into three well separated peaks, termed alpha, beta, gamma. These peaks are shown to correspond to differently charged forms of MLCK with the charge difference between alpha and beta twice as large as between beta and gamma. The isoelectric point and elution position of the peaks as well as their amplitudes are modified by phosphorylation or by autophosphorylation of MLCK suggesting that the observed charge differences are related to their different phosphate content. The three forms appear to have similar apparent affinity for both the substrates, ATP and the isolated regulatory light chain, but their specific activities are different.
Dalla Libera
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Dipartimento Scienze Biomediche Sperimentali, Università di Padova, Italy.
Mastroianni
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M
Sobieszek
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A
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D000838:Anions; D002645:Chickens; D002851:Chromatography, High Pressure Liquid; D005895:Gizzard, Avian / Q000201:enzymology; D007526:Isoelectric Point; D007700:Kinetics; D009130:Muscle, Smooth / Q000201:enzymology*; D009219:Myosin-Light-Chain Kinase / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D009218:Myosins / Q000378:metabolism; D010710:Phosphates / Q000032:analysis; D010766:Phosphorylation; D013379:Substrate Specificity; D014422:Turkeys
D000838:Anions; D010710:Phosphates; D000255:Adenosine Triphosphate; D009219:Myosin-Light-Chain Kinase; D009218:Myosins