| Abstrakt: |
Rhodobacter capsulatus fixes CO via the Calvin reductive pentose phosphate pathway and, like some other nonsulfur purple bacteria, is known to synthesize two distinct structural forms of ribulose 1,5-bisphosphate carboxylase/oxygenase (RubisCO). Cosmid clones that hybridized to form I ( cbbLcbbS) and form II ( cbbM) RubisCO gene probes were isolated from a genomic library of R. capsulatus strain SB1003. Southern blotting and hybridization analysis with gene-specific probes derived from Rhodobacter sphaeroides revealed that R. capsulatus cbbM is clustered with genes encoding other enzymes of the Calvin cycle, including fructose 1,6/sedoheptulose 1,7-bisphosphatase ( cbbF), phosphoribulokinase ( cbbP), transketolase ( cbbT), glyceraldehyde-3-phosphate dehydrogenase ( cbbG), and fructose 1,6-bisphosphate aldolase ( cbbA), as well as a gene ( cbbR) encoding a divergently transcribed LysR-type regulatory protein. Surprisingly, a cosmid clone containing the R. capsulatus form I RubisCO genes ( cbbL and cbbS) failed to hybridize to the other cbb structural gene probes, unlike the situation with the closely related organism R. sphaeroides. The form I and form II RubisCO genes were cloned into pUC-derived vectors and were expressed in Escherichia coli to yield active recombinant enzyme in each case. Complementation of a RubisCO-deletion strain of R. sphaeroides to photosynthetic growth by R. capsulatus cbbLcbbS or cbbM was achieved using the broad host-range vector, pRK415, and R. sphaeroides expression vector pRPS-1. [ABSTRACT FROM AUTHOR] |
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