Cooperativity of thiol-modified myosin filaments. ATPase and motility assays of myosin function.
Cooperativity of thiol-modified myosin filaments. ATPase and motility assays of myosin function.
复制标题
硫醇修饰的肌球蛋白丝的协同性。
DOI：
10.1016/s0006-3495(92)81646-6
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发表时间：
1992
影响因子：
3.4
通讯作者：
Reisler,E
中科院分区：
文献类型：
--
作者：
Root,DD;Reisler,E
本工作研究了肌球蛋白活性半胱氨酸的化学修饰对肌动球蛋白腺苷三磷酸酶（ATP酶）活性和体外运动试验中滑动速度的影响。研究的三种类型的修饰是SH 2的4-[N-[（碘乙酰氧基）乙基]-N-甲氨基]-7-硝基苯并-2-氧杂-1，3-二唑标记（基于Ajtai和Burghart. 1989.生物化学。28：2204-2210.），SH 1的苯基马来酰亚胺标记，以及在严格条件下肌原纤维中肌球蛋白的苯基马来酰亚胺标记。在运动试验中，每种类型的修饰肌球蛋白都抑制肌动蛋白的滑动。肌动蛋白的滑动速度超过共聚物的改性和未改性的肌球蛋白的运动性测定是最慢的rigor改性的肌球蛋白和最快的SH 2标记的肌球蛋白。肌动蛋白激活的ATP酶活性的类似共聚肌球蛋白最低的SH 2标记的肌球蛋白和最高的rigor修改的肌球蛋白。肌动蛋白激活的ATP酶活性的肌球蛋白亚片段-1从这些修饰的肌球蛋白以相同的线性方式减少与修改头的分数。这些结果被解释使用一个模型，其中肌动蛋白丝的滑动肌球蛋白丝的肌动蛋白激活的可能性降低。肌动蛋白的滑动速度超过单体刚性改性的肌球蛋白超过了丝状形式，这表明这种肌球蛋白的细丝结构是重要的运动试验中的肌动蛋白滑动的抑制。事实上，所有的半胱氨酸修饰检查抑制肌动球蛋白ATP酶的活动和肌动蛋白的肌球蛋白的滑动速度提出了有关的信息激活的横桥连接到肌球蛋白上的SH 1或SH 2的探针。
The effects of chemical modifications of myosin's reactive cysteines on actomyosin adenosine triphosphatase (ATPase) activities and sliding velocities in the in vitro motility assays were examined in this work. The three types of modifications studied were 4-[N-[(iodoacetoxy)ethyl]-N-methylamino]-7-nitrobenz-2-oxa-1,3- diazole labeling of SH2 (based on Ajtai and Burghart. 1989. Biochemistry. 28:2204–2210.), phenylmaleimide labeling of SH1, and phenylmaleimide labeling of myosin in myofibrils under rigor conditions. Each type of modified myosin inhibited the sliding of actin in motility assays. The sliding velocities of actin over copolymers of modified and unmodified myosins in the motility assay were slowest with rigor-modified myosin and most rapid with SH2-labeled myosin. The actin-activated ATPase activities of similarly copolymerized myosins were lowest with SH2-labeled myosin and highest with rigor-modified myosin. The actin-activated ATPase activities of myosin subfragment-1 obtained from these modified myosins decreased in the same linear manner with the fraction of modified heads. These results are interpreted using a model in which the sliding of actin filaments over myosin filaments decreases the probability of myosin activation by actin. The sliding velocity of actin over monomeric rigor-modified myosin exceeded that over the filamentous form, which suggests for this myosin that filament structure is important for the inhibition of actin sliding in motility assays. The fact that all cysteine modifications examined inhibited the actomyosin ATPase activities and sliding velocities of actin over myosin poses questions concerning the information about the activated crossbridge obtained from probes attached to SH1 or SH2 on myosin.