Glavas N A, Hou C, Bragg P D
Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, Canada.
Biochem Biophys Res Commun. 1995 Sep 5;214(1):230-8. doi: 10.1006/bbrc.1995.2279.
The proton-translocating transmembrane pyridine nucleotide transhydrogenase of Escherichia coli is composed of two types of subunits, alpha and beta. The beta subunit has several membrane-spanning segments in the N-terminal region followed by a cytosolic C-terminal domain bearing a binding site for NADP(H). The N-terminal region contains at least one residue involved in the process of transmembrane proton translocation. Using site-directed mutagenesis cysteine residues were introduced at selected sites into the N-terminal region of the beta subunit. The pattern of labelling of these residues with 3-(N-maleimidyl propionyl)biocytin and other sulfhydryl reagents has shown that a model in which the N-terminal region of the beta subunit spans the membrane in eight segments is more likely than a previously proposed six segment model (Holmberg et al. (1994) Biochemistry 33, 7691-7700). The preferred model accounts for the site of labelling of a glutamate residue (Glu124) in the N-terminal domain by N,N-dicyclohexylcarbodiimide.
大肠杆菌的质子转运跨膜吡啶核苷酸转氢酶由α和β两种亚基组成。β亚基在N端区域有几个跨膜片段，后面是一个胞质C端结构域，带有一个NADP(H)结合位点。N端区域包含至少一个参与跨膜质子转运过程的残基。通过定点诱变，在β亚基的N端区域的选定位置引入了半胱氨酸残基。用3-(N-马来酰亚胺基丙酰基)生物素和其他巯基试剂对这些残基进行标记的模式表明，β亚基的N端区域以八个片段跨膜的模型比先前提出的六个片段模型更有可能（霍尔姆伯格等人（1994年）《生物化学》33卷，7691 - 7700页）。优选模型解释了N，N-二环己基碳二亚胺对N端结构域中一个谷氨酸残基（Glu124）的标记位点。
