Increased site 1 affinity improves biopotency of porcine growth hormone - Evidence against diffusion dependent receptor dimerization

Wan, Y., McDevitt, A., Shen, B. J., Smythe, M. L. and Waters, M. J. (2004) Increased site 1 affinity improves biopotency of porcine growth hormone - Evidence against diffusion dependent receptor dimerization. Journal of Biological Chemistry, 279 43: 44775-44784. doi:10.1074/jbc.M406092200

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Author Wan, Y.
McDevitt, A.
Shen, B. J.
Smythe, M. L.
Waters, M. J.
Title Increased site 1 affinity improves biopotency of porcine growth hormone - Evidence against diffusion dependent receptor dimerization
Journal name Journal of Biological Chemistry   Check publisher's open access policy
ISSN 0021-9258
Publication date 2004-01-01
Sub-type Article (original research)
DOI 10.1074/jbc.M406092200
Open Access Status File (Publisher version)
Volume 279
Issue 43
Start page 44775
End page 44784
Total pages 10
Place of publication Bethesda
Publisher American Society for Biochemistry and Molecular Biology, Inc.
Language eng
Subject C1
630100 Livestock
270103 Protein Targeting and Signal Transduction
Abstract Based on phage display optimization studies with human growth hormone (GH), it is thought that the biopotency of GH cannot be increased. This is proposed to be a result of the affinity of the first receptor for hormone far exceeding that which is required to trap the hormone long enough to allow diffusion of the second receptor to form the ternary complex, which initiates signaling. We report here that despite similar site 1 kinetics to the hGH/hGH receptor interaction, the potency of porcine GH for its receptor can be increased up to 5-fold by substituting hGH residues involved in site 1 binding into pGH. Based on extensive mutations and BIAcore studies, we show that the higher potency and site 1 affinity of hGH for the pGHR is primarily a result of a decreased off-rate associated with residues in the extended loop between helices 1 and 2 that interact with the two key tryptophans Trp(104) and Trp(169) in the receptor binding hot spot. Our mutagenic analysis has also identified a second determinant (Lys(165)), which in addition to His(169), restricts the ability of non-primate hormones to activate hGH receptor. The increased biopotency of GH that we observe can be explained by a model for GH receptor activation where subunit alignment is critical for effective signaling.
Keyword Biochemistry & Molecular Biology
Colony-stimulating Factor
Extracellular Domain
Monoclonal-antibody
Potency
Alpha
Erythropoietin
Aspartate
Mechanism
Residues
Epitope
Q-Index Code C1

 
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Created: Wed, 15 Aug 2007, 14:46:15 EST