Haemoprotein b-590 (Escherichia coli); redesignation of a bacterial 'cytochrome a1'

A 'soluble' fraction from anaerobically grown Escherichia coli contains a haemoprotein with spectral properties, notably an alpha-band in the reduced form at 585 to 595 nm, similar to cytochrome a1. Haem extraction of either the soluble preparation or whole cells yields haem b, but not haem a. In view of this, and the spectral similarities of the a1-like component to well-known high-spin haem b proteins, we propose that the name 'haemoprotein b-590' be used to describe cytochrome a1-like pigments in bacteria.