Referenced in: none

Automatically associated channels: Kir2.3

Title: Glycine as a D-amino acid surrogate in the K(+)-selectivity filter.

Authors: Francis I Valiyaveetil, Matthew Sekedat, Roderick MacKinnon, Tom W Muir

Journal, date & volume: Proc. Natl. Acad. Sci. U.S.A., 2004 Dec 7 , 101, 17045-9

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/15563591

Abstract
The K(+) channel-selectivity filter consists of two absolutely conserved glycine residues. Crystal structures show that the first glycine in the selectivity filter, Gly-77 in KcsA, is in a left-handed helical conformation. Although the left-handed helical conformation is not favorable for the naturally occurring L-amino acids, it is favorable for the chirally opposite D-amino acids. Here, we demonstrate that Gly-77 can be replaced by D-Ala with almost complete retention of function. In contrast, substitution with an L-amino acid results in a nonfunctional channel. This finding suggests that glycine is used as a surrogate D-amino acid in the selectivity filter. The absolute conservation of glycine in the K(+)-selectivity filter can be explained as a result of glycine being the only natural amino acid that can play this role.