Linked Life Data

1104358

Source:http://linkedlifedata.com/resource/pubmed/id/1104358

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
2
pubmed:dateCreated
1976-3-1
pubmed:abstractText
Experiments were devised to test the plausibility and the predictions of a efflux rate equation which was previously derived [10]9 1. 2-Keto-3-deoxy-D-gluconate transport system conforms with universal laws relating zero-trans influx, influx at steady-state, steady-state levels of accumulation to external and internal substrate concentrations. 2. Full-time-course uptake kinetics fit the linearized graphical representation that can be inferred from the integrated rate equation. 3. Influx does not depend upon internal substrate concentration nor upon energy-coupling. 4. Zero-trans outflux (leak inot empty medium) is a first-order process (rate constant: 0.02 min-1) and not mediated by the carrier. Absence of cis-competition with D-glucuronate is in agreement with a simple diffusion mechanism. 5. Outflux increases when external substrate concentration is raised (counterflow). Outflux at steady-state equilibrates influx, and is a first-order process (rate constant: 0.15 min-1). 6. Uncoupling with azide leads to accelerate zero-trans outflux by a factor of 2-3. No further acceleration is obtained when other classical uncouplers are used. The process remains first-order, independent of the amount of carrier, and is accelerated by the presence of internal D-glucuronate as a result from trans-inhibition of the recapture. 7. Exchange outflux is all the more accelerated by azide as the carrier is less saturated. The process is clearly carrier-mediated and the outflux rate obeys a Michaelis law with respect to internal concentration. V is equal to V for influx. 8. Homo and hetero-overshoot experiments are in agreement with the participation of the carrier for mediating influx as well as outflux. 9. The kinetics of D-glucuronate outflux in a strain lacking the specific hexuronate permease but carrying the 2-keto-3-deoxy-D-glucuronate permease are similar to those obtained with 2-keto-3-deoxy-D-gluconate. We draw the conclusion that energy-coupling promotes the adjustment of outflux without interfering with influx rate. It apparently acts by reducing, in a continuous range, the affinity of the carrier facing inwards. The discussion is focused on the comparison with previously published models and on possible molecular mechanisms.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jul
pubmed:issn
0014-2956
pubmed:author
pubmed:issnType
Print
pubmed:day
1
pubmed:volume
55
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
343-54
pubmed:dateRevised
2009-10-27
pubmed:meshHeading
pubmed:year
1975
pubmed:articleTitle
The energy-coupling controlled efflux of 2-keto-3-deoxy-D-gluconate in Escherichia coli K 12.
pubmed:publicationType
Journal Article