FTSH IS REQUIRED FOR PROTEOLYTIC ELIMINATION OF UNCOMPLEXED FORMS OF SECY, AN ESSENTIAL PROTEIN TRANSLOCASE SUBUNIT

被引:213
作者
KIHARA, A
AKIYAMA, Y
ITO, K
机构
[1] Department of Cell Biology, Institute for Virus Research, Kyoto University
关键词
PROTEIN TRANSLOCATION; QUALITY CONTROL; PROTEOLYSIS; AAA FAMILY; MEMBRANE PROTEIN;
D O I
10.1073/pnas.92.10.4532
中图分类号
O [数理科学和化学]; P [天文学、地球科学]; Q [生物科学]; N [自然科学总论];
学科分类号
07 ; 0710 ; 09 ;
摘要
When secY is overexpressed over secE or secE is underexpressed, a Fraction of SecY protein is rapidly degraded in vivo. This proteolysis was unaffected in previously described protease-defective mutants examined, We found, however, that some mutations in ftsH, encoding a membrane protein that belongs to the AAA (ATPase associated with a variety of cellular activities) family, stabilized oversynthesized SecY. This stabilization was due to a loss of FtsH function, and overproduction of the wild-type FtsH protein accelerated the degradation. The ftsH mutations also suppressed, by alleviating proteolysis of an altered form of SecY, the temperature sensitivity of the secY24 mutation, which alters SecY such that its interaction with SecE is weakened and it is destabilized at 42 degrees C. We were able to isolate a number of additional mutants with decreased ftsH expression or with an altered form of FtsH using selection/screening based on suppression of secY24 and stabilization of oversynthesized SecY. These results indicate that FtsH is required for degradation of SecY. Overproduction of SecY in the ftsH mutant cells proved to deleteriously affect cell growth and protein export, suggesting that elimination of uncomplexed SecY is important for optimum protein translocation and for the integrity of the membrane. The primary role of FtsH is discussed in light of the quite pleiotropic mutational effects, which now include stabilization of uncomplexed SecY.
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页码:4532 / 4536
页数:5
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