Linked Life Data

3146350

Source:http://linkedlifedata.com/resource/pubmed/id/3146350

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
23
pubmed:dateCreated
1989-3-23
pubmed:abstractText
Two mutant versions of Escherichia coli aspartate transcarbamylase were created by site-specific mutagenesis. Arg-234 of the 240s loop was replaced by serine in order to help deduce the function of the interactions that normally occur between Arg-234 and both Glu-50 and Gln-231 in the R state of the enzyme. The other mutation involved the replacement of Asp-271 by asparagine to further test the functional importance of the Tyr-240-Asp-271 link that has previously been proposed to stabilize the T state of the enzyme [Middleton, S. A., & Kantrowitz, E. R. (1986) Proc. Natl. Acad. Sci. U.S.A. 83, 5866-5870]. The Arg-234----Ser holoenzyme exhibits no cooperativity, a 24-fold reduction in maximal velocity, normal affinity for carbamyl phosphate, and substantially reduced affinity for aspartate and N-(phosphonoacetyl)-L-aspartate (PALA). Unlike the wild-type enzyme, the heterotropic effectors ATP and CTP are able to influence the activity of the Arg-234----Ser enzyme at saturating aspartate concentrations. The Arg-234----Ser catalytic subunit exhibits a 33-fold reduction in maximal activity, an aspartate Km of 261 mM, compared to 5.7 mM for the wild-type catalytic subunit, and only a small alteration in the Km for carbamyl phosphate. Together these results provide additional evidence that the interdomain bridging interactions between Glu-50 of the carbamyl phosphate domain and both Arg-167 and Arg-234 of the aspartate domain are necessary for the stabilization of the high-activity-high-affinity configuration of the active site of the enzyme. Furthermore, without the interdomain bridging interactions, the holoenzyme no longer exhibits homotropic cooperativity.(ABSTRACT TRUNCATED AT 250 WORDS)
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Nov
pubmed:issn
0006-2960
pubmed:author
pubmed:issnType
Print
pubmed:day
15
pubmed:volume
27
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
8653-60
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed:year
1988
pubmed:articleTitle
Function of arginine-234 and aspartic acid-271 in domain closure, cooperativity, and catalysis in Escherichia coli aspartate transcarbamylase.
pubmed:affiliation
Department of Chemistry, Boston College, Chestnut Hill, Massachusetts 02167.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S.