Linked Life Data

2495283

Source:http://linkedlifedata.com/resource/pubmed/id/2495283

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
11
pubmed:dateCreated
1989-5-18
pubmed:abstractText
Our studies, which are aimed at understanding the catalytic mechanism of the beta subunit of tryptophan synthase from Salmonella typhimurium, use site-directed mutagenesis to clarify the functional roles of several putative active site residues. Although previous chemical modification studies have suggested that histidine 86, arginine 148, and cysteine 230 are essential residues in the beta subunit, our present findings that beta subunits with single amino acid replacements at these positions have partial activity show that these 3 residues are not essential for catalysis or substrate binding. These conclusions are consistent with the recently determined three-dimensional structure of the tryptophan synthase alpha 2 beta 2 complex. Amino acid substitution of lysine 87, which forms a Schiff base with pyridoxal phosphate in the wild type beta subunit, yields an inactive form of the beta subunit which binds alpha subunit, pyridoxal phosphate, and L-serine. We also report a rapid and efficient method for purifying wild type and mutant forms of the alpha 2 beta 2 complex from S. typhimurium from an improved enzyme source. The enzyme, which is produced by a multicopy plasmid encoding the trpA and trpB genes of S. typhimurium expressed in Escherichia coli, is crystallized from crude extracts by the addition of 6% poly(ethylene glycol) 8000 and 5 mM spermine. This new method is also used in the accompanying paper to purify nine alpha 2 beta 2 complexes containing mutant forms of the alpha subunit.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Apr
pubmed:issn
0021-9258
pubmed:author
pubmed:issnType
Print
pubmed:day
15
pubmed:volume
264
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
6280-7
pubmed:dateRevised
2000-12-18
pubmed:meshHeading
pubmed:year
1989
pubmed:articleTitle
The beta subunit of tryptophan synthase. Clarification of the roles of histidine 86, lysine 87, arginine 148, cysteine 170, and cysteine 230.
pubmed:affiliation
Section on Pharmacology, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, Maryland 20892.
pubmed:publicationType
Journal Article