Improvement of the 2.5 A resolution model of cytochrome b562 by redetermining the primary structure and using molecular graphics.

Abstract The amino acid sequence of cytochrome b 562 has been redetermined and fitted to a 2.5 A electron density map. A combination of cyanogen bromide fragmentation, proteolytic cleavages and manual and automatic sequencing was used. The model was built on an MMS-X molecular graphics system by interactively fitting the model to the electron density. The results indicate that the protein is 106 rather than 110 residues in length. The largest change required has been the rearrangement and modification of a continuous stretch of 11 residues of the original sequence. The electron density map confirms most of these changes, some of which were proposed before the revised sequence became available.