PURIFICATION OF 2 PRESSURE-REGULATED C-TYPE CYTOCHROMES FROM A DEEP-SEA BAROPHILIC BACTERIUM, SHEWANELLA SP. STRAIN DB-172F

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.