Crystallization and preliminary X-ray analysis of two pH-dependent forms of cytochrome c(2) from Rhodopseudomonas palustris

Cytochrome c(2) from Rhodopseudomonas palustris has been crystallized in tw o different crystal forms: a monoclinic form I at pH 4.4 from both reduced and oxidized protein solution and a trigonal form II at pH 9.0 from reduced protein solution. Complete 1.7 and 1.4 Angstrom resolution data sets were collected from the oxidized form I and from the form II, respectively. The preliminary structures show an important change in the iron coordination en vironment in the trigonal form obtained at basic pH arising from the substi tution of the Met ligand by an ammonia molecule.