InterPro domain: IPR011044

Quinohemoprotein amine dehydrogenase (QHNDH) from Paracoccus denitrificans is a heterotrimer consisting of alpha, beta and gamma chains [ 1 ]. The alpha chain has a four-domain structure that includes a dihaem cytochrome c, the beta chain forms a 7-bladed beta-propeller that is part of the enzyme active site, and the gamma chain contains the redox factor cysteine tryptophylquinone (CTQ).

The beta chain of QHNDH structurally resembles the 7-bladed beta propeller of the H chain of the periplasmic quinoprotein methylamine dehydrogenase (MADH), found in methylotrophic bacteria [ 2 ]. MADH is a heterotetramer consisting of two heavy (H) chains and two light (L) chains, and contains the redox cofactor tryptophan tryptophylquinone (TTQ). There is no similarity between the quinone-containing chains of MAD and QHNDH.

The beta-propeller structure found in MAD and QHNDH is similar to the YVTN (Tyr-Val-Thr-Asn) repeat that folds into a beta-propeller found in the N-terminal domain of archaeal surface layer proteins, which help protect cells from extreme environments [ 3 ].

1. Structure of a quinohemoprotein amine dehydrogenase with an uncommon redox cofactor and highly unusual crosslinking. Proc. Natl. Acad. Sci. U.S.A. 98, 14268-73
2. Refined crystal structure of methylamine dehydrogenase from Paracoccus denitrificans at 1.75 A resolution. J. Mol. Biol. 276, 131-49
3. Archaeal surface layer proteins contain beta propeller, PKD, and beta helix domains and are related to metazoan cell surface proteins. Structure 10, 1453-64