Assembly of the Stator in Escherichia coli ATP Synthase. Complexation of Subunit with Other F1 Subunits Is Prereq

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• 作者：Alan E. Senior ; Alma Muharemagi//pubs.acs.org/images/entities/cacute.gif" border="0"> ; Susan Wilke-Mounts
• 刊名：Biochemistry
• 出版年：2006
• 出版时间：December 26, 2006
• 年：2006
• 卷：45
• 期：51
• 页码：15893 - 15902
• 全文大小：122K
• 年卷期：v.45,no.51(December 26, 2006)
• ISSN：1520-4995

文摘

images/gifchars/alpha.gif" BORDER=0> subunit of Escherichia coli ATP synthase was expressed with a C-terminal 6-His tag andpurified. Pure images/gifchars/alpha.gif" BORDER=0> was monomeric, was competent in nucleotide binding, and had normal N-terminal sequence.In F₁ subunit dissociation/reassociation experiments it supported full reconstitution of ATPase, andreassociated complexes were able to bind to F₁-depleted membranes with restoration of ATP-driven protonpumping. Therefore interaction between the stator images/gifchars/delta.gif" BORDER=0 > subunit and the N-terminal residue 1-22 region ofimages/gifchars/alpha.gif" BORDER=0> occurred normally when pure images/gifchars/alpha.gif" BORDER=0> was complexed with other F₁ subunits. On the other hand, three differenttypes of experiments showed that no interaction occurred between pure images/gifchars/delta.gif" BORDER=0 > and isolated images/gifchars/alpha.gif" BORDER=0> subunit. Unlikein F₁, the N-terminal region of isolated images/gifchars/alpha.gif" BORDER=0> was not susceptible to trypsin cleavage. Therefore, during assemblyof ATP synthase, complexation of images/gifchars/alpha.gif" BORDER=0> subunit with other F₁ subunits is prerequisite for images/gifchars/delta.gif" BORDER=0 > subunit bindingto the N-terminal region of images/gifchars/alpha.gif" BORDER=0>. We suggest that the N-terminal 1-22 residues of images/gifchars/alpha.gif" BORDER=0> are sequestered inisolated images/gifchars/alpha.gif" BORDER=0> until released by binding of images/gifchars/beta2.gif" BORDER=0 ALIGN="middle"> to images/gifchars/alpha.gif" BORDER=0> subunit. This prevents 1/1 images/gifchars/delta.gif" BORDER=0 >/images/gifchars/alpha.gif" BORDER=0> complexes from forming andprovides a satisfactory explanation of the stoichiometry of one images/gifchars/delta.gif" BORDER=0 > per three images/gifchars/alpha.gif" BORDER=0> seen in the F₁ sector of ATPsynthase, assuming that steric hindrance prevents binding of more than one images/gifchars/delta.gif" BORDER=0 > to the images/gifchars/alpha.gif" BORDER=0>3/images/gifchars/beta2.gif" BORDER=0 ALIGN="middle">3 hexagon. Thecytoplasmic fragment of the b subunit (b_sol) did not bind to isolated images/gifchars/alpha.gif" BORDER=0>. It might also be that complexationof images/gifchars/alpha.gif" BORDER=0> with images/gifchars/beta2.gif" BORDER=0 ALIGN="middle"> subunits is prerequisite for direct binding of stator b subunit to the F₁-sector.