Myosin rod protein: a novel thick filament component of Drosophila muscle.
Myosin rod protein: a novel thick filament component of Drosophila muscle.
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DOI：
10.1006/jmbi.1996.0710
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发表时间：
1997-01
影响因子：
5.6
通讯作者：
D. Standiford;M. Davis;K. Miedema;C. Franzini-armstrong;C. Emerson
中科院分区：
文献类型：
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作者：
D. Standiford;M. Davis;K. Miedema;C. Franzini-armstrong;C. Emerson
肌球蛋白棒蛋白（MRP）是由果蝇肌球蛋白重链（Mhc）基因内部的一个基因编码的155 kDa的蛋白，包含Mhc棒结构域，但具有77个独特的n端残基，正好取代Mhc马达和轻链结合结构域。最初被描述为一种丰富的睾丸蛋白，我们现在证明MRP也是果蝇肌丝的主要成分。具体来说，Mrp启动子指导LacZ报告基因在躯体、心脏和内脏肌肉中的表达。mrp特异性抗体检测肌肉提取物中洗涤剂不溶性部分的蛋白质，并将蛋白质与MHC共定位到免疫染色肌肉中的肌共聚a带。免疫印迹分析显示，在一组成人直飞肌（DFM）中，MRP与MHC的比例为1:3。用0.5 M氯化钾提取粗丝蛋白进行化学交联和共免疫沉淀实验表明，天然MRP为同二聚体。MRP含量高的DFM49在电镜下，横切面肌丝排列紊乱，细丝与粗丝的比值变化，纵切面细丝严重弯曲，与粗丝的关联不明显。严格地说，来自DFM49的粗细丝由带有交叉桥的片段组成，这些交叉桥穿插着缺乏交叉桥的光滑结构域。这些数据表明，MRP是一种新型的收缩蛋白，它与肌球蛋白共同整合到粗丝中，从而改变了肌节的结构和功能。
Myosin rod protein (MRP), a 155 kDa protein encoded by a gene internal to the Drosophila muscle myosin heavy chain (Mhc) gene, contains the MHC rod domain, but has 77 unique N-terminal residues that exactly replace the MHC motor and light chain binding domains. Originally described as an abundant testis protein, we now demonstrate the MRP also is a major component of myofilaments in Drosophila. Specifically, the Mrp promoter directs the expression of a LacZ reporter transgene in somatic, cardiac and visceral muscles. MRP-specific antibodies detect the protein in detergent-insoluble fractions of muscle extracts and co-localize the protein with MHC to the sarcomeric A-band in immunostained muscles. Immunoblot analysis shows that in a set of adult direct flight muscles (DFM), the ratio of MRP to MHC is 1:3. Chemical cross-link and co-immunoprecipitation experiments using 0.5 M KCl-extracted thick filament proteins indicate that native MRP is a homodimer. Electron microscopy of DFM49, which has a high MRP content, shows in cross section, disordered myofilament packing and a variable thin to thick filament ratio and, in longitudinal section, severely bent thin filaments that are not well associated with thick filaments. In rigor, thick filaments from DFM49 consist of segments with cross bridges that are interspersed with smooth domains lacking cross bridges. These data indicate that MRP is a novel contractile protein that co-integrates with myosin into the thick filament, thereby changing structure and function of the sarcomere.