Linked Life Data

1287657

Source:http://linkedlifedata.com/resource/pubmed/id/1287657

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
8
pubmed:dateCreated
1993-3-16
pubmed:abstractText
Active site residues of ricin A chain were analyzed by site-directed mutagenesis and X-ray diffraction to help assess their roles in the mechanism of action of this toxic N-glycosidase enzyme. Arg180 is thought, from X-ray studies, to protonate the adenine substrate at N3; this facilitates bond cleavage and is crucial to the mechanisms of action. The residue was converted to Gln and initial rate data measured. Km for the mutant is not significantly affected, increasing only 2-fold. The kcat, however, is decreased approximately 1000-fold. This is consistent with a simple interpretation that Arg180 is involved more in transition state stabilization than in substrate binding. Tyrosines 80 and 123 are known from X-ray models to stack on either side of the substrate adenine ring. When they were each converted to serine overall activity was reduced 160- and 70-fold respectively against ribosomes from Artemia salina. These effects are each approximately 10 times greater than when the residues were previously converted to phenylalanines. Sufficient protein for the Tyr80 to Phe mutant was obtained to carry out an X-ray analysis. Together with mutagenesis data, the structure suggests that the invariance of the two active site Tyr residues is largely caused by structural stability.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Dec
pubmed:issn
0269-2139
pubmed:author
pubmed:issnType
Print
pubmed:volume
5
pubmed:geneSymbol
rta
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
775-9
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed:year
1992
pubmed:articleTitle
Analysis of several key active site residues of ricin A chain by mutagenesis and X-ray crystallography.
pubmed:affiliation
Clayton Foundation Biochemical Institute, Department of Chemistry and Biochemistry, University of Texas, Austin 78712.
pubmed:publicationType
Journal Article, Comparative Study, Research Support, U.S. Gov't, P.H.S., Research Support, Non-U.S. Gov't