Glycine as a d-amino acid surrogate in the K+-selectivity filter
AUTOR(ES)
Valiyaveetil, Francis I.
FONTE
National Academy of Sciences
RESUMO
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.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=535378Documentos Relacionados
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