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首页> 外文期刊>Biochemistry >Two distinct mechanisms for regulation of nonmuscle myosin assembly via the heavy chain: phosphorylation for MIIB and mts 1 binding for MIIA.
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Two distinct mechanisms for regulation of nonmuscle myosin assembly via the heavy chain: phosphorylation for MIIB and mts 1 binding for MIIA.

机译：通过重链调节非肌球蛋白组装的两种不同机制：MIIB的磷酸化和MIIA的mts 1结合。

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摘要

In search of the regulation mechanisms for isoform specific myosin assembly, we have used the COOH-terminal fragments of nonmuscle myosin isoforms MIIA and MIIB (MIIA(F46) and MIIB(alpha)(F47)) as a model system. Phosphorylation by protein kinase C (PK C) or casein kinase II (CK II) within or near the nonhelical tail-end domain inhibits assembly of MIIB(alpha)(F47) [Murakami, N., et al. (1998) Biochemistry 37, 1989]. In the study presented here, we mutated the kinase sites to analyze the inhibition mechanisms of MIIB assembly by phosphorylation. Replacement of the CK II or PK C sites with Asp (MIIB(alpha)(F47)-CK-5D or -PK-4D) strongly inhibited the filament assembly, with or without Mg(2+), by significantly increasing the critical concentrations for assembly. Without Mg(2+), MIIB(alpha)(F47)-CK-5D or -PK-4D inhibited the assembly of wild-type (wt) MIIB(alpha)(F47) by either mixing as homofragments or forming heterofragments. With 2.5 mM Mg(2+), MIIB(alpha)(F47)-wt promoted assembly of MIIB(alpha)(F47)-CK-5D and -PK-4D in homofragment mixtures, but not by forming heterofragments. MIIA(F46) coassembled with MIIB(alpha)(F47)-wt and -CK-5D and altered their assembly patterns. In contrast, assembly of MIIB(alpha)(F47)-PK-4D was unchanged by MIIA(F46). A metastasis-associated protein, mts 1, bound in a Ca(2+)-dependent manner to MIIA(F46), but not appreciably to MIIB(alpha)(F47). At 0.15 M NaCl, mts 1-Ca(2+) not only inhibited MIIA(F46) assembly but also disassembled the MIIA(F46) filaments. Mts 1, however, did not affect the assembly of MIIB(alpha)(F47) in MIIA(F46) and MIIB(alpha)(F47) mixtures, indicating that mts 1 is an inhibitor specific to MIIA assembly. Our results suggest strongly that assembly of MIIA and MIIB is regulated by distinct mechanisms via tail-end domains: phosphorylation of MIIB and mts 1 binding to MIIA. These mechanisms may also function to form MIIA or MIIB homofilaments by selectively inhibiting MIIB or MIIA assembly.
机译：在寻找同工型特异性肌球蛋白装配的调节机制时，我们使用了非肌肉型肌球蛋白同工型MIIA和MIIB的COOH末端片段（MIIA（F46）和MIIBα（F47））作为模型系统。非螺旋尾端结构域内或附近的蛋白激酶C（PK C）或酪蛋白激酶II（CK II）进行的磷酸化抑制了MIIBα（F47）的组装[Murakami，N.等。 （1998）Biochemistry 37，1989]。在这里提出的研究中，我们突变了激酶位点以通过磷酸化分析MIIB组装的抑制机制。用Asp（MIIBα（F47）-CK-5D或-PK-4D）取代CK II或PK C位点可通过显着增加临界浓度来强烈抑制有或没有Mg（2+）的灯丝组件用于组装。在没有Mg（2+）的情况下，MIIBα（F47）-CK-5D或-PK-4D通过混合为同片段或形成异片段来抑制野生型（wt）MIIBα（F47）的装配。使用2.5 mM的Mg（2 +），MIIBα（F47）-wt促进了MIIBα（F47）-CK-5D和-PK-4D在同片段混合物中的组装，但没有形成异片段。 MIIA（F46）与MIIBα（F47）-wt和-CK-5D共同组装，并改变了它们的组装方式。相反，MIIA（F46）没有改变MIIBα（F47）-PK-4D的装配。转移相关蛋白mts 1以Ca（2+）依赖方式与MIIA（F46）结合，但与MIIBα（F47）无关。在0.15 M NaCl中，mts 1-Ca（2+）不仅抑制MIIA（F46）组装，而且还拆解了MIIA（F46）细丝。然而，Mts 1不会影响MIIA（F46）和MIIBα（F47）混合物中MIIBα（F47）的组装，表明Mts 1是MIIA组装特有的抑制剂。我们的研究结果强烈表明，MIIA和MIIB的组装受末端域的独特机制所调节：MIIB的磷酸化和与MIIA结合的mts 1。这些机制还可通过选择性抑制MIIB或MIIA组装来形成MIIA或MIIB均丝。

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