Premium
The involvement of NAD(P)H dehydrogenase subunits, NdhD3 and NdhF3, in high‐affinity CO 2 uptake in Synechococcus sp. PCC7002 gives evidence for multiple NDH‐1 complexes with specific roles in cyanobacteria
Author(s) -
Klughammer Barbara,
Sültemeyer Dieter,
Badger Murray R.,
Price G. Dean
Publication year - 1999
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.1999.01457.x
Subject(s) - biology , protein subunit , synechococcus , nadh dehydrogenase , mutant , biochemistry , nad+ kinase , cyanobacteria , gene , microbiology and biotechnology , enzyme , genetics , bacteria
Random gene tagging was used to obtain new mutants of the marine cyanobacterium, Synechococcus sp. PCC7002, with defects in the CO 2 ‐concentrating mechanism (CCM). Two of these mutants, K22 and A41, showed poor growth at limiting CO 2 . Isolation and sequencing of a 6.6 kb genomic region revealed the existence of five potential protein‐coding regions, all arranged in the same transcriptional direction. These regions code for an RbcR homologue, NdhF3 (subunit 5 of type 1 NAD(P)H dehydrogenase; NDH‐1 complex), NdhD3 (subunit 4 of NDH‐1), ORF427 and ORF133 (hypothetical proteins). Insertional mutants in ndhD3 , ndhF3 and ORF427 , like A41 and K22, were all incapable of inducing high‐affinity CO 2 uptake and were not fully capable of inducing high‐affinity HCO 3 − transport. ndhD3 and ndhF3 mutants displayed P700 re‐reduction rates identical to wild‐type cells, suggesting that NdhD3 is part of a specific NDH‐1 complex that is not involved in photosynthetic cyclic electron transport. Thus, it is feasible that NdhD3, NdhF3 and ORF427 might form part of a novel NDH‐1 complex located on the cytoplasmic membrane and involved in tightly coupled energization of high‐affinity CO 2 transport. The possibility of multiple, functionally distinct NDH‐1 complexes in cyanobacteria is discussed.