Hassell T C, Kemp B E, Masaracchia R A
Biochem Biophys Res Commun. 1986 Jan 14;134(1):240-7. doi: 10.1016/0006-291x(86)90553-x.
Thymus myosin, light chains and a synthetic peptide (S-S-K-R-A-K-A-K-T-T-K-K-R-P-Q-R-A-T-S-N-V-F-S) corresponding to the N-terminal sequence of smooth muscle myosin light chains were compared as substrates for calcium/calmodulin-dependent protein kinase (MLCK), calcium/phospholipid-dependent protein kinase (PKC), and a MgATP-activated protein kinase (H4PK) from lymphoid cells. All protein kinases catalyzed phosphorylation of the substrates although H4PK showed higher affinity for isolated light chains and the peptide. Phosphoamino acid analysis and analysis of thermolysin peptides established that PKC catalyzed phosphorylation of threonine-9 or 10. In addition, PKC and H4PK catalyzed phosphorylation at serine-19, the MLCK site. Collectively the data support the hypothesis that myosin filament assembly in nonmuscle cells may be regulated by a variety of calcium-dependent and calcium-independent protein kinases.
胸腺肌球蛋白、轻链以及对应平滑肌肌球蛋白轻链N端序列的合成肽（S-S-K-R-A-K-A-K-T-T-K-K-R-P-Q-R-A-T-S-N-V-F-S）作为钙/钙调蛋白依赖性蛋白激酶（肌球蛋白轻链激酶，MLCK）、钙/磷脂依赖性蛋白激酶（蛋白激酶C，PKC）以及来自淋巴细胞的MgATP激活蛋白激酶（H4PK）的底物进行了比较。所有蛋白激酶均催化底物的磷酸化，尽管H4PK对分离的轻链和肽表现出更高的亲和力。磷酸氨基酸分析和嗜热菌蛋白酶肽段分析确定PKC催化苏氨酸-9或10的磷酸化。此外，PKC和H4PK催化丝氨酸-19（MLCK作用位点）的磷酸化。总体而言，这些数据支持以下假设：非肌肉细胞中的肌球蛋白丝组装可能受多种钙依赖性和非钙依赖性蛋白激酶的调节。
