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Proteins. 1992 May;13(1):41-56.

Comparative analysis of the beta transducin family with identification of several new members including PWP1, a nonessential gene of Saccharomyces cerevisiae that is divergently transcribed from NMT1.

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Department of Molecular Biology and Pharmacology, Washington University School of Medicine, St. Louis, Missouri 63110.


While investigating the expression of the Saccharomyces cerevisiae myristoyl-CoA:protein N-myristoyltransferase gene (NMT: E.C. by Northern blot analysis, we observed another RNA transcript whose expression resembled that of NMT1 during meiosis and was derived from a gene located less than 1 kb immediately upstream of NMT1. This new gene, designated PWP1 (for periodic tryptophan protein), is divergently transcribed from NMT1 and encodes a 576-residue protein. Null mutants of PWP1 are viable, but their growth is severely retarded and steady-state levels of several cellular proteins (including at least two proteins that label with exogenous [3H]myristic acid) are drastically reduced. New methods for database searching and assessing the statistical significance of sequence similarities identify PWP1 as a member of the beta-transducin protein superfamily. Two other previously unrecognized beta-transducin-like proteins (S. cerevisiae MAK11 and D. discoideum AAC3) were also identified, and an unexpectedly high degree of sequence homology was found between a Chlamydomonas beta-like polypeptide and the C12.3 gene of chickens. A systematic and quantitative comparative analysis resulted in classifying all beta-transducin-like sequences into 11 nonorthologous families. Based on specific sequence attributes, however, not all beta-transducin-like sequences are expected to be functionally similar, and quantitative criteria for inferring functional analogies are discussed. Possible roles of repetitive tryptophan residues in proteins are also considered.

[Indexed for MEDLINE]

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