104l

From Proteopedia

Revision as of 13:43, 12 November 2007

HOW AMINO-ACID INSERTIONS ARE ALLOWED IN AN ALPHA-HELIX OF T4 LYSOZYME

Overview

Studies of extant protein sequences indicate that amino-acid insertions, and deletions are preferentially located in loop regions, which has, traditionally been explained as the result of selection removing, deleterious mutations within secondary structural elements from the, population. But there is no a priori reason to discount the possibility, that insertions within secondary structure could either be tolerated until, compensatory mutations arise, or have effects that are propagated away, from secondary structure into loops. Earlier studies have indicated that, insertions are generally tolerated, although much less well within, secondary structure elements than in loop regions. Here we show that, amino-acid insertions in an alpha-helix of T4 lysozyme can be accepted in, two different ways. In some cases the inserted amino acids are, accommodated within the helix, leading to the translocation of wild-type, residues from the helix to the preceding loop. In other cases the, insertion causes a 'looping-out' in the first or last turn of the helix., The individual structural responses seem to be dominated by the, maintenance of the interface between the helix and the rest of the, protein.

About this Structure

104L is a Single protein structure of sequence from Enterobacteria phage t2. Full crystallographic information is available from OCA.

Reference

How amino-acid insertions are allowed in an alpha-helix of T4 lysozyme., Heinz DW, Baase WA, Dahlquist FW, Matthews BW, Nature. 1993 Feb 11;361(6412):561-4. PMID:8429913

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