Linked Life Data

21168419

Source:http://linkedlifedata.com/resource/pubmed/id/21168419

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
1
pubmed:dateCreated
2011-1-28
pubmed:databankReference
pubmed:abstractText
Solute receptors (binding proteins) are indispensable components of canonical ATP-binding cassette importers in prokaryotes. Here, we report on the characterization and crystal structures in the closed and open conformations of AcbH, the solute receptor of the putative carbohydrate transporter AcbFG which is encoded in the acarbose (acarviosyl-1,4-maltose) biosynthetic gene cluster from Actinoplanes sp. SE50/110. Binding assays identified AcbH as a high-affinity monosaccharide-binding protein with a dissociation constant (K(d)) for ?-d-galactopyranose of 9.8±1.0 nM. Neither galactose-containing di- and trisaccharides, such as lactose and raffinose, nor monosaccharides including d-galacturonic acid, l-arabinose, d-xylose and l-rhamnose competed with [(1)(4)C]galactose for binding to AcbH. Moreover, AcbH does not bind d-glucose, which is a common property of all but one d-galactose-binding proteins characterized to date. Strikingly, determination of the X-ray structure revealed that AcbH is structurally homologous to maltose-binding proteins rather than to glucose-binding proteins. Two helices are inserted in the substrate-binding pocket, which reduces the cavity size and allows the exclusive binding of monosaccharides, specifically ?-d-galactopyranose, in the (4)C(1) conformation. Site-directed mutagenesis of three residues from the binding pocket (Arg82, Asp361 and Arg362) that interact with the axially oriented O4-H hydroxyl of the bound galactopyranose and subsequent functional analysis indicated that these residues are crucial for galactose binding. To our knowledge, this is the first report of the tertiary structure of a solute receptor with exclusive affinity for ?-d-galactopyranose. The putative role of a galactose import system in the context of acarbose metabolism in Actinoplanes sp. is discussed.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Feb
pubmed:issn
1089-8638
pubmed:author
pubmed:copyrightInfo
Copyright © 2010 Elsevier Ltd. All rights reserved.
pubmed:issnType
Electronic
pubmed:day
11
pubmed:volume
406
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
92-105
pubmed:meshHeading
pubmed:year
2011
pubmed:articleTitle
Crystal structures of the bacterial solute receptor AcbH displaying an exclusive substrate preference for ?-D-galactopyranose.
pubmed:affiliation
Institut für Biologie, AG Bakterienphysiologie, Humboldt Universität zu Berlin, Chausseestr. 117, D-10115 Berlin, Germany.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't