FIG. 2.

Separation of periplasmic cytochromes of R. capsulatus PAS100 and MC101. One-liter cultures of R. capsulatus PAS100 and MC101 were grown photosynthetically in RCV-malate, and the periplasmic extract from each culture was isolated. Each of these extracts was loaded onto a 1.7- by 15-cm DEAE-Sepharose CL6B anion-exchange column, and the columns were developed with an NaCl gradient in 100 mM Tris-HCl (pH 8). The figure shows the cytochrome absorbance (A₄₁₀) profile during the elution of proteins from columns loaded with each of these periplasmic extracts, PAS100 (filled circles) and MC101 (open circles). [NaCl] is marked by a dotted line. The first cytochrome to elute is cytochrome c₂, which is found in both strains. A second cytochrome, which has the spectral properties of cytochrome c′ (data not shown), eluted with 70 mM NaCl from columns loaded with PAS100 extract but not extracts from the cycP mutant strain MC101.