103L

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

Summary for 103L

• Entry DOI: 10.2210/pdb103l/pdb
• Descriptor: T4 LYSOZYME, CHLORIDE ION, BETA-MERCAPTOETHANOL, ... (4 entities in total)
• Functional Keywords: hydrolase(o-glycosyl)
• Biological source: Enterobacteria phage T4
• Total number of polymer chains: 1
• Total formula weight: 19092.73

Authors

Heinz, D.W.,Matthews, B.W. (deposition date: 1992-09-29, release date: 1993-10-31, Last modification date: 2024-02-07)

Primary citation

Heinz, D.W.,Baase, W.A.,Dahlquist, F.W.,Matthews, B.W.
How amino-acid insertions are allowed in an alpha-helix of T4 lysozyme.
Nature, 361:561-564, 1993

PubMed Abstract: 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.

PubMed: 8429913
DOI: 10.1038/361561a0

Experimental method

X-RAY DIFFRACTION (1.9 Å)