Evidence that SecB enhances the activity of SecA

被引:10
作者
Kim, J
Miller, A
Wang, LG
Müller, JP
Kendall, DA [1 ]
机构
[1] Univ Connecticut, Dept Mol & Cell Biol, Storrs, CT 06269 USA
[2] Univ Jena, Inst Mol Biol, D-07745 Jena, Germany
关键词
D O I
10.1021/bi002617z
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
In Escherichia coli, SecA is a critical component of the protein transport machinery which powers the translocation process by hydrolyzing ATP and recognizing signal peptides which are the earmark of secretory proteins. In contrast, SecB is utilized by only a subset of preproteins to prevent their premature folding and chaperone them to membrane-bound SecA. Using purified components and synthetic signal peptides, we have studied the interaction of SecB with SecA and with SecA-signal peptide complexes in vitro. Using a chemical cross-linking approach, we find that the formation of SecA-SecB complexes is accompanied by a decrease in the level of cross-linking of SecA dimers, suggesting that SecB induces a conformational change in SecA. Furthermore, functional signal peptides, but not dysfunctional ones, promote the formation of SecA-SecB complexes. SecB is also shown to directly enhance the ATPase activity of SecA in a concentration-dependent and saturable manner. To determine the biological consequence of this finding, the influence of SecB on the signal peptide-stimulated SecA/lipid ATPase was studied using synthetic peptides of varying hydrophobicity. Interestingly, the presence of SecB can sufficiently boost the response of signal peptides with moderate hydrophobicity such that it is comparable to the activity generated by a more hydrophobic peptide in the absence of SecB. The results suggest that SecB directly enhances the activity of SecA and provide a biochemical basis for the enhanced transport efficiency of preproteins in the presence of SecB in vivo.
引用
收藏
页码:3674 / 3680
页数:7
相关论文
共 33 条
[1]  
AKITA M, 1990, J BIOL CHEM, V265, P8164
[2]  
BRADFORD MM, 1976, ANAL BIOCHEM, V72, P248, DOI 10.1016/0003-2697(76)90527-3
[3]   MUTATIONS THAT IMPROVE EXPORT OF MALTOSE-BINDING PROTEIN IN SECB- CELLS OF ESCHERICHIA-COLI [J].
COLLIER, DN ;
BASSFORD, PJ .
JOURNAL OF BACTERIOLOGY, 1989, 171 (09) :4640-4647
[4]   THE ANTIFOLDING ACTIVITY OF SECB PROMOTES THE EXPORT OF THE ESCHERICHIA-COLI MALTOSE-BINDING PROTEIN [J].
COLLIER, DN ;
BANKAITIS, VA ;
WEISS, JB ;
BASSFORD, PJ .
CELL, 1988, 53 (02) :273-283
[5]   A SIGNAL SEQUENCE IS NOT REQUIRED FOR PROTEIN EXPORT IN PRLA MUTANTS OF ESCHERICHIA-COLI [J].
DERMAN, AI ;
PUZISS, JW ;
BASSFORD, PJ ;
BECKWITH, J .
EMBO JOURNAL, 1993, 12 (03) :879-888
[6]   Kinetic partitioning - Poising SecB to favor association with a rapidly folding ligand [J].
Diamond, DL ;
Randall, LL .
JOURNAL OF BIOLOGICAL CHEMISTRY, 1997, 272 (46) :28994-28998
[7]   TITRATION OF PROTEIN-TRANSPORT ACTIVITY BY INCREMENTAL CHANGES IN SIGNAL PEPTIDE HYDROPHOBICITY [J].
DOUD, SK ;
CHOU, MM ;
KENDALL, DA .
BIOCHEMISTRY, 1993, 32 (05) :1251-1256
[8]   Preprotein transfer to the Escherichia coli translocase requires the co-operative binding of SecB and the signal sequence to SecA [J].
Fekkes, P ;
de Wit, JG ;
van der Wolk, JPW ;
Kimsey, HH ;
Kumamoto, CA ;
Driessen, AJM .
MOLECULAR MICROBIOLOGY, 1998, 29 (05) :1179-1190
[9]   DIFFUSION-LIMITED INTERACTION BETWEEN UNFOLDED POLYPEPTIDES AND THE ESCHERICHIA-COLI CHAPERONE SECB [J].
FEKKES, P ;
DENBLAAUWEN, T ;
DRIESSEN, AJM .
BIOCHEMISTRY, 1995, 34 (31) :10078-10085
[10]   The molecular chaperone SecB is released from the carboxy-terminus of SecA during initiation of precursor protein translocation [J].
Fekkes, P ;
vanderDoes, C ;
Driessen, AJM .
EMBO JOURNAL, 1997, 16 (20) :6105-6113