Dc. Brune, ISOLATION AND CHARACTERIZATION OF SULFUR GLOBULE PROTEINS FROM CHROMATIUM-VINOSUM AND THIOCAPSA-ROSEOPERSICINA, Archives of microbiology, 163(6), 1995, pp. 391-399
Purple sulfur bacteria store sulfur as intracellular globules enclosed
by a protein envelope. The proteins associated with sulfur globules o
f Chromatium vinosum and Thiocapsa roseopersicina were isolated by ext
raction into 50% aqueous acetonitrile containing 1% trifluoroacetic ac
id and 10 mM dithiothreitol. The extracted proteins were separated by
reversed-phase HPLC, revealing three major proteins from C. vinosum an
d two from T. roseopersicina. All of these proteins have similar, rath
er unusual amino acid compositions, being rich in glycine and aromatic
amino acids, particularly tyrosine. The molecular masses of the C. vi
nosum proteins were determined to be 10,498, 10,651, and 8,479 Da, whi
le those from T. roseopersicina were found to be 10,661 and 8,759 Da b
y laser desorption time-of-flight mass spectrometry. The larger T. ros
eopersicina protein is N-terminally blocked, probably by acetylation,
but small amounts of the unblocked form (mass = 10,619) were also isol
ated by HPLC. Protein sequencing showed that the two larger C. vinosum
proteins are homologous to each other and to the large T. roseopersic
ina protein. The 8,479 Da C. vinosum and 8,759 Da T. roseopersicina si
cina proteins are also homologous, indicating that sulfur globule prot
eins are conserved between different species of purple sulfur bacteria
.