Linked Life Data

3316227

Source:http://linkedlifedata.com/resource/pubmed/id/3316227

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
35
pubmed:dateCreated
1988-1-21
pubmed:abstractText
The mechanism of melibiose symport by the melibiose permease of Escherichia coli was studied by looking at the modifications of the facilitated diffusion properties of the permease which arise upon substitution of the coupled cations (H+, Na+, or Li+). Kinetic analysis of melibiose influx and efflux down a concentration gradient, exchange at equilibrium, and counterflow were examined in de-energized membrane vesicles resuspended in media allowing melibiose to be co-transported with either H+, Na+, or Li+. The data show that the maximal rates of melibiose efflux coupled to either H+, Na+, or Li+ are between 10 and 40 times faster than the corresponding influxes. This suggests that the permease functions asymmetrically. Cross-comparison between the rates of net [3H]melibiose entry during the influx reactions coupled to either cation and corresponding unidirectional sugar inflow during exchange and counterflow reactions leads to the conclusions that: 1) the step involving release of the co-substrates from the permease on the inner surface of the membrane is sequenced (sugar first and then coupled cation); 2) this step is rate determining for cycling of the permease. The Na+-melibiose passive flux data indicate in particular that release of Na+ ions rather than release of sugar into the intravesicular space is the slowest step during permease cycling. This property would hamper net passive Na+-melibiose influx but should allow exchange of sugar without concomitant exchange of the coupled cation. Finally, evidence is provided suggesting that the relative rates of release of the two co-substrates from the permease on the inner membrane surface varied considerably in relation to the identity of the coupled cation.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Dec
pubmed:issn
0021-9258
pubmed:author
pubmed:issnType
Print
pubmed:day
15
pubmed:volume
262
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
16865-70
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
1987
pubmed:articleTitle
Facilitated diffusion properties of melibiose permease in Escherichia coli membrane vesicles. Release of co-substrates is rate limiting for permease cycling.
pubmed:affiliation
Laboratoire Jean Maetz, Département de Biologie du Commissariat à l'Energie Atomique, Villefranche-sur-Mer, France.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't