In:
Journal of Bacteriology, American Society for Microbiology, Vol. 191, No. 10 ( 2009-05-15), p. 3265-3272
Abstract:
In addition to the ATP-binding cassette (ABC)-type nitrate/nitrite-bispecific transporter, which has a high affinity for both substrates ( K m , ∼1 μM), Synechococcus elongatus has an active nitrite transport system with an apparent K m (NO 2 − ) value of 20 μM. We found that this activity depends on the cynABD genes, which encode a putative cyanate (NCO − ) ABC-type transporter. Accordingly, nitrite transport by CynABD was competitively inhibited by NCO − with a K i value of 0.025 μM. The transporter was induced under conditions of nitrogen deficiency, and the induced cells showed a V max value of 11 to 13 μmol/mg of chlorophyll per h for cyanate or nitrite, which could supply ∼30% of the amount of nitrogen required for optimum growth. Its relative specificity for the substrates and regulation at transcriptional and posttranslational levels suggested that the physiological role of the bispecific cyanate/nitrite transporter in S. elongatus is to allow nitrogen-deficient cells to assimilate low concentrations of cyanate in the medium. Its contribution to nitrite assimilation was significant in a mutant lacking the ABC-type nitrate/nitrite transporter, suggesting a possible role for CynABD in nitrite assimilation by cyanobacterial species that lack another high-affinity mechanism(s) for nitrite transport.
Type of Medium:
Online Resource
ISSN:
0021-9193
,
1098-5530
Language:
English
Publisher:
American Society for Microbiology
Publication Date:
2009
detail.hit.zdb_id:
1481988-0
SSG:
12
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