The porin RafY encoded by the raffinose plasmid pRSD2 of Escherichia coli forms a general diffusion pore and not a carbohydrate-specific porin

被引:14
作者
Andersen, C [1 ]
Krones, D
Ulmke, C
Schmid, K
Benz, R
机构
[1] Univ Wurzburg, Theodor Boveri Inst, Biozentrum, Lehrstuhl Biotechnol, D-97074 Wurzburg, Germany
[2] Univ Osnabruck, Fachbereich Biol Chem, Arbeitsgrp Genet, D-4500 Osnabruck, Germany
来源
EUROPEAN JOURNAL OF BIOCHEMISTRY | 1998年 / 254卷 / 03期
关键词
raffinose transport; carbohydrate specificity; RafY channel; enteric bacteria; lipid bilayer membrane;
D O I
10.1046/j.1432-1327.1998.2540679.x
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
The gene rafY from the plasmid pRSD2, which enables Escherichia coli to grow on raffinose, was transferred into expression plasmid pUSL77. The protein was expressed in the porin-deficient Escherichia coli strain KS26 and was isolated and purified to homogeneity. The pure protein was reconstituted into lipid bilayer membranes. It formed an ion-permeable channel with a single-channel conductance of 2.9 nS of the open state in 1 M KCl, which is approximately twice of that of the general diffusion pores OmpF and OmpC of E. coli outer membrane. At lower pH the channel exhibited rapid flickering between three substates of the open channel. The RafY channel appears to be wide and water filled and has a small selectivity for cations over anions. Although RafY is part of an uptake and fermentation system for raffinose it does not contain a binding site for carbohydrates. Our results suggest that RafY is a general diffusion pore with a diameter, larger than that of the general diffusion porins OmpF and OmpC, that allows the diffusion of high-molecular-mass carbohydrates through the outer membrane.
引用
收藏
页码:679 / 684
页数:6
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