Linked Life Data

1633151

Source:http://linkedlifedata.com/resource/pubmed/id/1633151

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
28
pubmed:dateCreated
1992-8-25
pubmed:abstractText
Barnase is found to have a series of subsites for binding its substrates that confers large rate enhancements. Ribonucleotide substrates of the type Zp0Gp1Xp2Y have been synthesized, where p is phosphate, X, Y, and Z are nucleosides, and G is guanosine. G occupies the primary specificity site. The most important subsite is for p2, followed by that for Y. There appears to be no subsite for the Z or p0 positions. Occupation of the subsite for p2 gives rise to a 1000-fold increase in kcat/Km, composed of a 100-fold increase in kcat and a 10-fold decrease in Km. The Y subsite gives rise to further 20-fold increase in kcat/Km. Rates approaching diffusion control for kcat/Km are observed. kcat for the dinucleotide monophosphate GpU = 0.55 s-1, and Km = 240 microM; this compares with 53 s-1 and 20 microM for GpUp, and 3.3 x 10(3) s-1 and 17 microM for GpApA (the best substrate tested). Cleavage occurs at the 3'-phosphate of guanosine in all cases. There are differences in base specificity at the two subsites for X and Y downstream of the scissile bond. The binding energies of different substrates have been analyzed using thermodynamic cycles. These show that the contributions of the X and Y sites are nonadditive.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jul
pubmed:issn
0006-2960
pubmed:author
pubmed:issnType
Print
pubmed:day
21
pubmed:volume
31
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
6390-5
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
1992
pubmed:articleTitle
Barnase has subsites that give rise to large rate enhancements.
pubmed:affiliation
Department of Chemistry, University of Cambridge, England.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't