Structure
Volume 10, Issue 4, April 2002, Pages 581-588
Journal home page for Structure

Article
Structure of the lac Operon Galactoside Acetyltransferase

https://doi.org/10.1016/S0969-2126(02)00741-4Get rights and content
Under an Elsevier user license
open archive

Abstract

The galactoside acetyltransferase (thiogalactoside transacetylase) of Escherichia coli (GAT, LacA, EC 2.3.1.18) is a gene product of the classical lac operon. GAT may assist cellular detoxification by acetylating nonmetabolizable pyranosides, thereby preventing their reentry into the cell. The structure of GAT has been solved in binary complexes with acetyl-CoA or CoA and in ternary complexes with CoA and the nonphysiological acceptor substrates isopropyl β-D-thiogalactoside (IPTG) or p-nitrophenyl β-D-galactopyranoside (PNPβGal). A hydrophobic cleft that binds the thioisopropyl and p-nitrophenyl aglycones of IPTG and PNPβGal may discriminate against substrates with hydrophilic substituents at this position, such as lactose, or inducers of the lac operon. An extended loop projecting from the left-handed parallel β helix domain contributes His115, which is in position to facilitate attack of the C6-hydroxyl group of the substrate on the thioester.

Keywords

crystal structure
acetyltransferase
transacetylase
coenzyme A
lactose operon
EC 2.3.1.18

Cited by (0)

2

Present address: Division of Geographic Medicine and Infectious Diseases, Department of Medicine, New England Medical Center, 750 Washington Street, Boston, Massachusetts 02111.