The high- and low-affinity receptor binding sites of growth hormone are allosterically coupled.

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TitleThe high- and low-affinity receptor binding sites of growth hormone are allosterically coupled.
Publication TypeJournal Article
Year of Publication2004
AuthorsWalsh, STR, Sylvester, JE, Kossiakoff, AA
JournalProc Natl Acad Sci U S A
Volume101
Issue49
Pagination17078-83
Date Published2004 Dec 7
ISSN0027-8424
KeywordsAllosteric Site, Binding Sites, Carrier Proteins, Human Growth Hormone, Humans, Hydrogen Bonding, Mutagenesis, Site-Directed, Protein Binding, Protein Conformation, Protein Structure, Secondary, Receptors, Somatotropin
Abstract

Growth hormone regulates its biological properties via a sequential hormone-induced receptor homodimerization mechanism. Using a mutagenesis-scanning analysis of 81 single and 32 pairwise double mutations, we show that the hormone's two spatially distal receptor binding sites (Site1 and Site2) are allosterically coupled. These allosteric effects are focused among a relatively few residues centered around the interaction between Asp-116 of the hormone and Trp-169 of the receptor in Site2. A rearrangement of this interaction triggered by mutations in Site1 produces both a major conformation and energetic reorganization of Site2, surprisingly without a reduction in overall binding affinity. Additionally, the data suggest a change in the conformational dynamics of several groups in Site2 that appear to be important in defining the Site2 interaction. Changes in binding energy of the affected Site2 residues usually range in magnitude from 3- to 60-fold, but in one case are as large as 10(4).

DOI10.1073/pnas.0403336101
Alternate JournalProc. Natl. Acad. Sci. U.S.A.
PubMed ID15563602
PubMed Central IDPMC535364
Grant ListDK-61602 / DK / NIDDK NIH HHS / United States