PROTON-COUPLED BIOENERGETIC PROCESSES IN EXTREMELY ALKALIPHILIC BACTERIA

被引:25
作者
KRULWICH, TA
GUFFANTI, AA
机构
[1] Department of Biochemistry, Mount Sinai School of Medicine of the City University of New York, New York, 10029
关键词
ALKALIPHILE; CYTOCHROMES; F1F0-ATPASE; OXIDATIVE PHOSPHORYLATION; PH REGULATION; SODIUM PROTON ANTIPORTER; SODIUM BINDING PROTEINS;
D O I
10.1007/BF00762351
中图分类号
Q6 [生物物理学];
学科分类号
071011 ;
摘要
Oxidative phosphorylation, which involves an exclusively proton-coupled ATP synthase, and pH homeostasis, which depends upon electrogenic antiport of cytoplasmic Na+ in exchange for H+, are the two known bioenergetic processes that require inward proton translocation in extremely alkaliphilic bacteria. Energy coupling to oxidative phosphorylation is particularly difficult to fit to a strictly chemiosmotic model because of the low bulk electrochemical proton gradient that follows from the maintenance of a cytoplasmic pH just above 8 during growth at pH 10.5 and higher. A large quantitative and variable discrepancy between the putative chemiosmotic driving force and the phosphorylation potential results. This is compounded by a nonequivalence between respiration-dependent bulk gradients and artificially imposed ones in energizing ATP synthesis, and by an apparent requirement for specific respiratory chain complexes that do not relate solely to their role in generation of bulk gradients. Special features of the synthase may contribute to the mode of energization, just as novel features of the Na+ cycle may relate to the extraordinary capacity of the extreme alkaliphiles to achieve pH homeostasis during growth at, or sudden shifts to, an external pH of 10.5 and above.
引用
收藏
页码:587 / 599
页数:13
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