Methionine acts as a “magnet” in photoaffinity crosslinking experiments

Edited by Irmgard Sinning

Received 2 January 2006; received in revised form 1 February 2006; accepted 16 February 2006. published online 23 February 2006.

Abstract

Photoaffinity crosslinking has been utilized to probe the nature of the ligand–receptor interface for a number of G protein-coupled receptor systems. Often the photoreactive benzophenone moiety incorporated in the ligand is found to react with a methionine in the receptor. We introduced methionines one-at-a-time into the region 163–176 of the parathyroid hormone receptor, and find that crosslinking occurs to the side-chain of methionine over a range of 11 amino acids. We call this the “Magnet Effect” of methionine. Hence, crosslinking contact points can be significantly shifted by the presence of methionine in a receptor domain.

Abbreviations: Bpa, p-benzoylphenylalanine, Bpan-PTH, [Bpan,Nle8,18,Arg13,26,27,L-2-Nal23,Tyr34]bPTH(1–34)NH2, CNBr, cyanogen bromide, Endo-F, endoglycosidase F/N-glycosidase F, N-ECD, N-terminal extracellular domain, Nle, norleucine, PTH, parathyroid hormone, PTHR1, PTH receptor-1

Keywords: Parathyroid hormone receptor-1, Photoaffinity crosslinking, Cyanogen bromide, Methionine scan, Site-directed mutagenesis

a Department of Physiology, Tufts University School of Medicine, 136 Harrison Ave, M&V 7, Boston, MA 02111, United States

b Departments of Chemistry and Molecular Pharmacology, Brown University, Providence, RI 02912, United States

Corresponding author. Fax: +1 617 636 0445.

PII: S0014-5793(06)00251-1

doi:10.1016/j.febslet.2006.02.050

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