Ja. Maupinfurlow et Jg. Ferry, ANALYSIS OF THE CO DEHYDROGENASE ACETYL-COENZYME-A SYNTHASE OPERON OFMETHANOSARCINA-THERMOPHILA/, Journal of bacteriology, 178(23), 1996, pp. 6849-6856
The cdhABC genes encoding the respective alpha, epsilon, and beta subu
nits of the five-subunit (alpha, beta, gamma, delta, and epsilon) CO d
ehydrogenase/acetyl-coenzyme synthase (CODH/ACS) complex from Methanos
arcina thermophila were cloned and sequenced. Northern (RNA) blot anal
yses indicated that the cdh genes encoding the five subunits and an op
en reading frame (ORF1) with unknown function are cotranscribed during
growth on acetate. Northern blot and primer extension analyses sugges
ted that mRNA processing and multiple promoters may be involved in edi
t transcript synthesis. The putative CdhA (alpha subunit) and CdhB (ep
silon subunit) proteins each have 40% identity to CdhA and CdhB of the
CODH/ACS complex from Methanosaeta soehngenii. The cdhC gene encodes
the beta subunit (CdhC) of the CODH/ACS complex from M. thermophila. T
he N-terminal 397 amino acids of CdhC are 42% identical to the C-termi
nal half of the or subunit of CODH/ACS from the acetogenic anaerobe Cl
ostridium thermoaceticum, Sequence analysis suggested potential struct
ures and functions for the previously uncharacterized beta subunit fro
m M. thermophila. The deduced protein sequence of ORF1, located betwee
n the cdhC and cdhD genes, has 29% identity to NifH2 from Methanobacte
rium ivanovii.