Linked Life Data

7857938

Source:http://linkedlifedata.com/resource/pubmed/id/7857938

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
7
pubmed:dateCreated
1995-3-22
pubmed:abstractText
We have studied the roles of metal cofactors Mg2+ and Mn2+ in modulating substrate specificities during the enzymatic cycle of TaqI endonuclease using steady state and single-turnover kinetics. In the presence of Mg2+, stringent discrimination of TaqI against single base-pair changes (star sites) is manifested by the loss of tight, specific binding in the early stage of the enzymatic cycle. In the presence of Mn2+, relaxed specificity for a star site sequence is attributed to formation of three distinct classes of the ternary complexes: the highly activated TaqI-cognate-Mn2+ complex; the partially activated TaqI-star-Mn2+ complex; and the ground state, inactive TaqI-nonspecific-Mn2+ complex. In addition to a high affinity for a TaqI-DNA complex, Mn2+ also binds to TaqI in a DNA-independent fashion. This may facilitate enzyme activation, which could account for the observed relaxation in substrate specificity. Thus, the TaqI-DNA-Mn2+ complex could be formed by either of two pathways: TaqI binding to DNA followed by the binding of Mn2+ or TaqI first binding to Mn2+ followed by the addition of DNA. The inactive, nonspecific TaqI-star-Mg2+ complex virtually prohibits transition state interactions, but a TaqI-star-Mn2+ complex attains a measurable single-turnover rate. In the late stages of the enzymatic cycle, high affinity of Mn2+ to a TaqI-DNA complex and to the TaqI enzyme may also account for a slower rate of product release.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Feb
pubmed:issn
0006-2960
pubmed:author
pubmed:issnType
Print
pubmed:day
21
pubmed:volume
34
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
2276-83
pubmed:dateRevised
2008-8-29
pubmed:meshHeading
pubmed:year
1995
pubmed:articleTitle
Stringent and relaxed specificities of TaqI endonuclease: interactions with metal cofactors and DNA sequences.
pubmed:affiliation
Department of Microbiology, Hearst Microbiology Research Center, Cornell University Medical College, New York, New York 10021.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S., Research Support, Non-U.S. Gov't