Linked Life Data

12468528

Source:http://linkedlifedata.com/resource/pubmed/id/12468528

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
10
pubmed:dateCreated
2003-3-3
pubmed:databankReference
pubmed:abstractText
BtuF is the periplasmic binding protein (PBP) for the vitamin B12 transporter BtuCD, a member of the ATP-binding cassette (ABC) transporter superfamily of transmembrane pumps. We have determined crystal structures of Escherichia coli BtuF in the apo state at 3.0 A resolution and with vitamin B12 bound at 2.0 A resolution. The structure of BtuF is similar to that of the FhuD and TroA PBPs and is composed of two alpha/beta domains linked by a rigid alpha-helix. B12 is bound in the "base-on" or vitamin conformation in a wide acidic cleft located between these domains. The C-terminal domain shares structural homology to a B12-binding domain found in a variety of enzymes. The same surface of this domain interacts with opposite surfaces of B12 when comparing ligand-bound structures of BtuF and the homologous enzymes, a change that is probably caused by the obstruction of the face that typically interacts with this domain by the base-on conformation of vitamin B12 bound to BtuF. There is no apparent pseudo-symmetry in the surface properties of the BtuF domains flanking its B12 binding site even though the presumed transport site in the previously reported crystal structure of BtuCD is located in an intersubunit interface with 2-fold symmetry. Unwinding of an alpha-helix in the C-terminal domain of BtuF appears to be part of conformational change involving a general increase in the mobility of this domain in the apo structure compared with the B12-bound structure. As this helix is located on the surface likely to interact with BtuC, unwinding of the helix upon binding to BtuC could play a role in triggering release of B12 into the transport cavity. Furthermore, the high mobility of this domain in free BtuF could provide an entropic driving force for the subsequent release of BtuF required to complete the transport cycle.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Mar
pubmed:issn
0021-9258
pubmed:author
pubmed:issnType
Print
pubmed:day
7
pubmed:volume
278
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
8429-34
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
2003
pubmed:articleTitle
Crystal structures of the BtuF periplasmic-binding protein for vitamin B12 suggest a functionally important reduction in protein mobility upon ligand binding.
pubmed:affiliation
Department of Biological Sciences, Columbia University, New York, New York 10027, USA.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S., Research Support, Non-U.S. Gov't