Binding of the Natural Killer Cell Inhibitory Receptor Ly49A to Its Major Histocompatibility Complex Class I Ligand

doi:10.1074/jbc.M110316200

Binding of the Natural Killer Cell Inhibitory Receptor Ly49A to Its Major Histocompatibility Complex Class I Ligand

CRUCIAL CONTACTS INCLUDE BOTH H-2D^d AND β₂-MICROGLOBULIN*

From the ^‡Molecular Biology Section, Laboratory of Immunology, NIAID, National Institutes of Health, Bethesda, Maryland 20892-1892, ^§Campus de la Universidad Autonoma de Madrid, 28049 Madrid, Spain, and ^¶Center for Advanced Research in Biotechnology, University of Maryland Biotechnology Institute, Rockville, Maryland 20850

Abstract

Ly49A, an inhibitory C-type lectin-like mouse natural killer cell receptor, functions through interaction with the major histocompatibility complex class I molecule, H-2D^d. The x-ray crystal structure of the Ly49A·H-2D^d complex revealed that homodimeric Ly49A interacts at two distinct sites of H-2D^d: Site 1, spanning one side of the α1 and α2 helices, and Site 2, involving the α1, α2, α3, and β₂m domains. Mutants of Ly49A, H-2D^d, and β₂-microglobulin at intermolecular contacts and the Ly49A dimer interface were examined for binding affinity and kinetics. Although mutations at Site 1 had little affect, several at Site 2 and at the dimer interface hampered the Ly49A·H-2D^d interaction, with no effect on gross structure or T cell receptor interaction. The region surrounding the most critical residues (in H-2D^d, Asp¹²²; in Ly49A, Asp²²⁹, Ser²³⁶, Thr²³⁸, Arg²³⁹, and Asp²⁴¹; and in β₂-microglobulin, Gln²⁹ and Lys⁵⁸) of the Ly49A·H-2D^d interface at Site 2 includes a network of water molecules, suggesting a molecular basis for allelic specificity in natural killer cell recognition.

Footnotes

↵* This work was supported in part by National Institutes of Health Grants AI47900 and GM52801 (to R. A. M.).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

This paper is dedicated to the memory of José Tormo, colleague and friend.
↵‖ To whom correspondence should be addressed: Molecular Biology Section, LI/NIAID, Bldg. 10, Rm. 11N311, National Institutes of Health, Bethesda, MD 20892-1892. Tel.: 301-496-6429; Fax: 301-496-0222; E-mail: dhm@nih.gov.
Published, JBC Papers in Press, November 5, 2001, DOI 10.1074/jbc.M110316200
↵2 N. Dimasi, M. W. Sawicki, L. N. Reineck, Y. Li, K. Natarajan, D. H. Margulies, and R. A. Mariuzza, manuscript in preparation.
Abbreviations:

NK

natural killer

β₂m

β₂-microglobulin

mAb

monoclonal antibody

MHC

major histocompatibility complex

TCR

T cell receptor

scTCR

single-chain T cell receptor

HIV

human immunodeficiency virus

MES

2-(N-morpholino)ethanesulfonic acid
- Received October 26, 2001.
The American Society for Biochemistry and Molecular Biology, Inc.