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Role of sequence bias in the topology of the multidrug transporter EmrE.


McHaourab HSHassane S , Mishra S Sanjay , Koteiche HA Hanane A , Amadi SH Sepan H . Biochemistry. 2008 8 5; 47(31). 7980-2


EmrE is the prototype of small multidrug resistance transporters and has emerged as a model of membrane protein evolution. Analysis of the distances separating symmetry-related site-specific spin labels, correlation of topological sequence bias to C-terminal orientation, to membrane insertion efficiency, and to resistance to ethidium bromide collectively demonstrate that EmrE monomers adopt a parallel topology in the functional dimer. We propose a coupled insertion and assembly model for EmrE in which the favorable energetics of the parallel dimer interface override topological constraints arising from weak asymmetry in positive charge distribution.