Association of tetrapyrrole intermediates in the bacteriochlorophyll a biosynthetic pathway with the major outer-membrane porin protein of Rhodobacter capsulatus.
Rhodobacter capsulatus regulates synthesis of bacteriochlorophyll a in response to changes in oxygen partial pressure and light intensity. One early model proposed that this regulation involved a carrier polypeptide that functions to tether tetrapyrrole intermediates to the membrane. In the present study we isolated tetrapyrrole intermediates accumulated in three strains of R. capsulatus that contain mutations which block bacteriochlorophyll a biosynthesis at different steps of the magnesium branch of the pathway. Each of the tetrapyrrole intermediates was shown to be associated with the same 32 kDa polypeptide, as indicated by similar electrophoretic mobility and antigenic cross-reactivity with polyclonal antisera. The 32 kDa pigment-associated protein was further found to have an electrophoretic mobility, antigenic cross-reactivity and N-terminal sequence identical with those of the previously characterized major outer-membrane porin protein of R. capsulatus.
Bollivar
D W
DW
Department of Biology, Indiana University, Bloomington 47405.
Bauer
C E
CE
D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism*; D001429:Bacteriochlorophylls / Q000096:biosynthesis*; D015153:Blotting, Western; D003429:Cross Reactions; D004591:Electrophoresis, Polyacrylamide Gel; D007473:Ion Channels / Q000378:metabolism*; D018272:Porins; D011758:Pyrroles / Q000378:metabolism*; D016354:Rhodobacter capsulatus / Q000378:metabolism*; D045725:Tetrapyrroles
D001425:Bacterial Outer Membrane Proteins; D001429:Bacteriochlorophylls; D007473:Ion Channels; D018272:Porins; D011758:Pyrroles; D045725:Tetrapyrroles