Effect of nucleotides, divalent cations and temperature on the tryptic susceptibility of myosin subfragment 1.
Effect of nucleotides, divalent cations and temperature on the tryptic susceptibility of myosin subfragment 1.
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核苷酸、二价阳离子和温度对肌球蛋白亚片段 1 胰蛋白酶敏感性的影响。
DOI：
10.1111/j.1432-1033.1984.tb08542.x
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发表时间：
1984
期刊：
影响因子：
--
通讯作者：
Gergely,J
中科院分区：
文献类型：
--
作者：
Mocz,G;Szilagyi,L;ChenLu,R;Fabian,F;Balint,M;Gergely,J
在21°C下，二价阳离子（Me 2+）和ATP、ADP、腺苷5′-[β，γ-亚氨基]三磷酸或PPi（含或不含Me 2+）改变了胰凝乳蛋白酶肌球蛋白亚片段1（S1）重链的胰蛋白酶分解动力学（其中数字代表近似质量，单位为kDa）。ATP或其类似物减慢步骤2并加速步骤3和4，而Me 2+加速步骤2。ATP及其类似物减少瞬时27-kDa肽的量[Hozumi，T. & Muhlrad，A.（1981）Biochemistry 20，2945-2950]。我们已经发现了直接证据，证明该参考文献中的建议，即27-kDa肽不是25-kDa片段的强制性前体，ATP或ADP抑制较大N-末端片段的形成，而不是加速其分解。位于20-kDa片段中的巯基的交联导致MgADP捕获在N-末端25-kDa肽中[威尔斯，J. A. & Yount，R. G.（1980）Biochemistry 19，1711-1717];该过程影响S1的胰蛋白酶片段化，类似于核苷酸，但不如核苷酸有效。Acts-S1的形成阻止了ATP对碎片化的影响。在37°C下，S1失去ATP酶活性;胰蛋白酶消化进行得更快，50-kDa和25-kDa片段被降解为小肽。核苷酸通过不仅在S1重链的27-kDa N-末端部分（含有推定的核苷酸结合位点）而且在50-kDa肽中产生构象变化来保护免受高温的影响。
The kinetics of tryptic breakdown of the heavy chain of chymotryptic myosin subfragment 1 (S1) according to the following scheme (where the numbers respresent approximate masses in kDa) are altered at 21°C by divalent cations (Me2+) and by ATP, ADP, adenosine 5′‐[β, γ‐imino]triphosphate or PPi, with or without Me2+. ATP or its analogs slow step 2 and accelerate steps 3 and 4, while Me2+accelerates step 2. ATP and its analogs decrease the amount of a transient 27‐kDa peptide [Hozumi, T. & Muhlrad, A. (1981)Biochemistry 20, 2945–2950]. We have found direct evidence for the suggestion in this reference that the 27‐kDa peptide is not an obligatory precursor of the 25‐kDa fragment and that ATP or ADP suppresses the formation of the larger N‐terminal fragment rather than accelerates its breakdown. Cross‐linking of sulfhydryl groups located in the 20‐kDa fragment leads to trapping of MgADP in the N‐terminal 25‐kDa peptide [Wells, J. A. & Yount, R. G. (1980)Biochemistry 19, 1711–1717]; this process affects the tryptic fragmentation of S1 similarly to, but less effectively than, nucleotides. Acts‐S1 formation prevents the effect of ATP on fragmentation. At 37°C S1 loses ATPase activity; tryptic digestion proceeds more rapidly and the 50‐kDa and 25‐kDa fragments are degraded to small peptides. Nucleotides protect against the effects of higher temperature by producing conformational changes not only in the 27‐kDa N‐terminal portion (containing the putative nucleotide binding site) of the heavy chain of S1 but also in the 50‐kDa peptide.