C-terminal lysine microheterogeneity and deamidation of Asn141 in the heavy chain and Asn161 in the light chain are the major causes of MMA383 charge heterogeneity. Identification of the two deamidation sites will allow replacement of these amino acids in order to create a product less susceptible to degradation.

No abstract

The α‐ and β‐apoproteins from the B800‐850‐complex of Rhodopseudomonas sphaeroides strain 2.4.1 have been sequenced. These results have been compared with those previously obtained with the analogous antenna apoproteins from the carotenoidless mutant R26.1 [9]. The α‐apoproteins differ at position 24, where a valine residue present in the wild‐type sequence is replaced by a phenylalanine residue in the mutant. The α‐apoproteins differ at the N‐terminus. In the wild‐type β‐apoprotein some chains have methionine at the N‐terminus and some have an N‐terminal threonine, while in the mutant the N‐terminus is threonine.

Four low-molecular-mass polypeptides were isolated and purified from chromatophore membranes of Rhodopseudomonas spliaeroides blue-green mutant R-26.

The complete amino acid sequence was determined for the ~1-and /?-chains of the B875 light-harvesting protein purified from photosynthetic membranes of Rhodopseudomonas sphaeroides 2.4.1. The sequence of the B875-a-polypeptide was identical to that reported for the R26.1 carotenoidless mutant [( 1985) B&him. Biophys. Acta 806, 185-1861 and contained 58 amino acid residues with a blocked methionine and a glutamic acid at the N-and C-termini, respectively. The B875$-polypeptide contained 48 amino acid residues with alanine and phenylalanine as respective N-and C-termini; although otherwise identical, the leucine at position 29 in the wild-type strain was replaced by proline in the mutant. This radical amino acid substitution occurred within the central hydrophobic domain of the /%polypeptide chain and is thought to result in a weakening of the structure of the a//? heterodimer since it was not possible to isolate the intact pigmentprotein complex from the R26.1 mutant strain. Amino acid sequence Light-harvesting protein Photosynthetic membrane Rhodopseudomonas sphaeroidesPolyacrylamide gel electrophoresis