Puustinen A, Wikström M
Helsinki Bioenergetics Group, Department of Medical Chemistry, Institute of Biomedical Sciences and Biocentrum Helsinki, P.O. Box 8, 00014 University of Helsinki, Helsinki, Finland.
Proc Natl Acad Sci U S A. 1999 Jan 5;96(1):35-7. doi: 10.1073/pnas.96.1.35.
Pathways of proton entry have been identified in the proton-translocating heme-copper oxidases, but the proton exit pathway is unknown. Here we report experiments with cytochrome bo3 in Escherichia coli cells that may identify the beginning of the exit pathway. Systematic mutations of arginines 438 and 439 (R481 and R482 in the E. coli enzyme), numbering as in cytochrome aa3 from bovine heart mitochondria, which interact with the ring D propionates of the two heme groups, reveal that the D propionate of the oxygen-binding heme is involved in proton pumping; its anionic form must be stabilized in order for proton translocation to occur. This may locate the beginning of the pathway by which pumped protons exit from the enzyme structure.
质子进入的途径已在质子转运血红素铜氧化酶中得到确认，但质子输出途径尚不清楚。在此，我们报告了在大肠杆菌细胞中对细胞色素bo3进行的实验，这些实验可能确定了输出途径的起点。对精氨酸438和439（大肠杆菌酶中的R481和R482，编号参照牛心线粒体细胞色素aa3）进行系统突变，它们与两个血红素基团的D环丙酸酯相互作用，结果表明，氧结合血红素的D环丙酸酯参与质子泵浦；其阴离子形式必须稳定，质子转运才能发生。这可能确定了被泵浦的质子从酶结构中输出的途径的起点。
