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Different protein sequences can give rise to highly similar folds through different stabilizing interactions
Author(s) -
Laurents D. V.,
Subbiah S.,
Levitt M.
Publication year - 1994
Publication title -
protein science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.353
H-Index - 175
eISSN - 1469-896X
pISSN - 0961-8368
DOI - 10.1002/pro.5560031105
Subject(s) - structural similarity , protein secondary structure , sequence (biology) , similarity (geometry) , helix (gastropod) , protein structure , threading (protein sequence) , loop modeling , crystallography , chemistry , protein structure prediction , biology , computer science , biochemistry , ecology , artificial intelligence , snail , image (mathematics)
We report an interesting case of structural similarity between 2 small, nonhomologous proteins, the third domain of ovomucoid (ovomucoid) and the C‐terminal fragment of ribosomal L7/L12 protein (CTF). The region of similarity consists of a 3‐stranded β‐sheet and an α‐helix. This region is highly similar; the corresponding elements of secondary structure share a common topology, and the RMS difference for “equivalent” Cα atoms is 1.6 Å. Surprisingly, this common structure arises from completely different sequences. For the common core, the sequence identity is less than 3%, and there is neither significant sequence similarity nor similarity in the position or orientation of conserved hydrophobic residues. This superposition raises the question of how 2 entirely different sequences can produce an identical structure. Analyzing this common region in ovomucoid revealed that it is stabilized by disulfide bonds. In contrast, the corresponding structure in CTF is stabilized in the α‐helix by a composition of residues with high helix‐forming propensities. This result suggests that different sequences and different stabilizing interactions can produce an identical structure.