Arrangement of domains, and amino acid residues required for binding of vascular cell adhesion molecule-1 to its counter-receptor VLA-4 (alpha 4 beta 1).
Interaction of the vascular cell adhesion molecule (VCAM-1) with its counter-receptor very late antigen-4 (VLA-4) (integrin alpha 4 beta 1) is important for a number of developmental pathways and inflammatory functions. We are investigating the molecular mechanism of this binding, in the interest of developing new anti-inflammatory drugs that block it. In a previous report, we showed that the predominant form of VCAM-1 on stimulated endothelial cells, seven-domain VCAM (VCAM-7D), is a functionally bivalent molecule. One binding site requires the first and the other requires the homologous immunoglobulin-like domain. Rotary shadowing and electron microscopy of recombinant soluble VCAM-7D molecules suggests that the seven Ig-like domains are extended in a slightly bent linear array, rather than compactly folded together. We have systematically mutagenized the first domain of VCAM-6D (a monovalent, alternately spliced version mission domain 4) by replacing 3-4 amino acids of the VCAM sequence with corresponding portions of the related ICAM-1 molecule. Specific amino acids, important for binding VLA-4 include aspartate 40 (D40), which corresponds to the acidic ICAM-1 residue glutamate 34 (E34) previously reported to be essential for binding of ICAM-1 to its integrin counter-receptor LFA-1. A small region of VCAM including D40, QIDS, can be replaced by the similar ICAM-1 sequence, GIET, without affecting function or epitopes, indicating that this region is part of a general integrin-binding structure rather than a determinant of binding specificity for a particular integrin. The VCAM-1 sequence G65NEH also appears to be involved in binding VLA-4.
Osborn
L
L
Biogen, Inc., Cambridge, Massachusetts 02142.
Vassallo
C
C
Browning
B G
BG
Tizard
R
R
Haskard
D O
DO
Benjamin
C D
CD
Dougas
I
I
Kirchhausen
T
T
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000737:chemistry; D000818:Animals; D000911:Antibodies, Monoclonal; D015815:Cell Adhesion Molecules / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D002460:Cell Line; D003001:Cloning, Molecular; D000939:Epitopes; D006801:Humans; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D016029:Receptors, Very Late Antigen / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D019010:Vascular Cell Adhesion Molecule-1
D000596:Amino Acids; D000911:Antibodies, Monoclonal; D015815:Cell Adhesion Molecules; D000939:Epitopes; D016029:Receptors, Very Late Antigen; D019010:Vascular Cell Adhesion Molecule-1