Department of Biological Structure, University of Washington, Seattle 98195.
The amino acid sequence of the copper-containing nitrite reductase (EC 1.7.99.3) from Achromobacter cycloclastes strain IAM 1013 has been determined by using peptides derived from digestion with Achromobacter protease I (Lys), Staphylococcus aureus V8 protease (Glu), cyanogen bromide, and BNPS-skatole in acetic acid. The subunit contains 340 amino acids. The identity of the first seven amino acids is tentative. The sequence has been instrumental in the X-ray structure determination of this molecule; in conjunction with the X-ray structure, ligands to a type I copper atom and a type II copper atom (one of each per subunit) have been identified. Comparison of the sequence to those of multi-copper oxidases such as ascorbate oxidase, laccase, and ceruloplasmin [Messerschmidt, A., & Huber, R. (1990) Eur. J. Biochem. 187, 341-352] reveals that each of two domains seen in the X-ray structure is similar to the oxidases and also to the small blue copper-containing proteins such as plastocyanin. The combination of sequence and structural similarity to ascorbate oxidase and sequence similarity to ceruloplasmin leads to a plausible model for the domain structure of ceruloplasmin.