title: Crystal structure of lactose permease in complex with an affinity inactivator yields unique insight into sugar recognition.
abstract: Lactose permease of Escherichia coli (LacY) with a single-Cys residue in place of A122 (helix IV) transports galactopyranosides and is specifically inactivated by methanethiosulfonyl-galactopyranosides (MTS-gal), which behave as unique suicide substrates. In order to study the mechanism of inactivation more precisely, we solved the structure of single-Cys122 LacY in complex with covalently bound MTS-gal. This structure exhibits an inward-facing conformation similar to that observed previously with a slight narrowing of the cytoplasmic cavity. MTS-gal is bound covalently, forming a disulfide bond with C122 and positioned between R144 and W151. E269, a residue essential for binding, coordinates the C-4 hydroxyl of the galactopyranoside moiety. The location of the sugar is in accord with many biochemical studies.
authors: Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA.
authors: Vincent
authors: V
authors: Chaptal
authors: Seunghyug
authors: S
authors: Kwon
authors: Michael R
authors: MR
authors: Sawaya
authors: Lan
authors: L
authors: Guan
authors: H Ronald
authors: HR
authors: Kaback
authors: Jeff
authors: J
authors: Abramson
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