The melibiose carrier of Escherichia coli: cysteine substitutions for individual residues in helix XI.

Autor:	Ding, P.Z., Wilson, T.H.
Předmět:	BIOLOGICAL membranes BIOLOGY ESCHERICHIA coli CYSTEINE proteinases MOLECULAR biology BIOMOLECULES BIOCHEMISTRY SODIUM metabolism CYSTEINE metabolism CYSTEINE RESEARCH BIOLOGICAL transport CELL membranes RESEARCH methodology EVALUATION research MEDICAL cooperation COMPARATIVE studies MEMBRANE transport proteins RESEARCH funding ION transport (Biology) AMINO acids DISACCHARIDES LITHIUM PHENOTYPES
Zdroj:	Journal of Membrane Biology; Mar2000, Vol. 174 Issue 2, p135-140, 6p
Abstrakt:	The melibiose carrier from Escherichia coli is a sugar-cation cotransport system. Previously evidence was obtained that this integral membrane protein consists of 12 transmembrane helices. Starting with the cysteine-less melibiose carrier, cysteine has been substituted individually for amino acids 374-396, which includes all of the residues in the proposed helix XI. The carriers with cysteine substitutions were studied for their transport activity and the effect of the water soluble sulfhydryl reagent p-chloromercuribenzenesulfonic acid (PCMBS). Studies were carried out on both intact cells and inside out vesicles. Cysteine substitution caused loss of transport activity in seven of the mutants (K377C, G379C, A383C, F385C, L391C, G395C and Y396C). PCMBS produced more than 50% inhibition in six of the mutants (S380C, A381C, A384C, F387C, A388C and L391C). Preincubation of the cells with melibiose protected five of these residues from the inhibitory action of PCMBS. It was concluded that the residues whose cysteine derivatives were inhibited by PCMBS probably faced the aqueous channel. [ABSTRACT FROM AUTHOR]
Databáze:	Complementary Index
Externí odkaz:	Full text from SpringerLink