From a deep-sea barophilic bacterium, Shewanella sp. strain DB-172F, a
membrane-bound cytochrome c-551 and a cytoplasmic cytochrome c-552 we
re purified. The cytochrome c-551 contained 44.7 nmol of heme c mg pro
tein(-1) and cytochrome c-552 contained 31.3 nmol of heme c mg protein
(-1). The CO difference spectrum of cytochrome c-551 showed a peak at
413.7 nm and troughs at 423.2, 522 and 552 nm which indicated that thi
s cytochrome combined with CO. Cytochrome c-551 was found to consist o
f two subunits with molecular masses of 29.1 kDa and 14.7 kDa, respect
ively, and each subunit contained one heme c molecule. Cytochrome c-55
2 also consisted of two subunits with molecular masses of 16.9 kDa and
14.7 kDa, respectively, and only one of these subunits contained heme
c. Cytochrome c-551 was constitutively synthesized when the cells wer
e grown at pressures of either 0.1 MPa or 60 MPa, whereas cytochrome c
-552 was synthesized only at 0.1 MPa. These results together with the
results of analysis of membrane-associated catalytic activities sugges
t that the respiratory system of DB-172F is regulated by pressure and
may be intimately related to the baroadaptability mechanism of this de
ep-sea bacterium. (C) 1998 Published by Elsevier Science B.V.