The N-terminal region and the mid-region complex of the integrin beta 2 subunit.
In the primary sequence of the integrin beta subunit, the N-terminal region (NTR) and mid-region are separated by the I-like domain. To determine the spatial relationship and functional properties of the integrin beta(2) NTR and mid-region, we constructed beta(2)/beta(7) chimeras in which the NTR, I-like domain, and the mid-region of the beta(2) subunit were replaced by those of beta(7). Changing either the beta(2) NTR or mid-region, but not the I-like domain to that of beta(7) did not affect LFA-1 (alpha(L)beta(2)) formation and surface expression. Thus, the specificity of alpha(L)beta(2) pairing is conferred by the I-like domain but not the NTR or mid-region. Using these chimeras, the epitopes of six anti-beta(2) mAbs (H52, 7E4, AZN-L18, AZN-L27, KIM202, and MEM-148) were mapped. All except H52 require both the NTR and mid-region for epitope expression. Since these mAbs have distinct properties in terms of epitope expression and effect on LFA-1 binding to ICAM-1, we conclude that the beta(2) NTR and mid-region interact extensively. Although the I-like domain is located between the NTR and mid-region, its removal does not affect the folding of the beta(2) NTR/mid-region complex because this complex alone can be expressed as a soluble protein and precipitated by the appropriate mAbs. Finally, the mAbs H52 and 7E4, abrogated KIM185- but not Mg/EGTAinduced LFA-1/ICAM-1 binding and the epitope of MEM-148 is expressed on Mg/EGTA-activated but not resting LFA-1. These results suggest that the NTR/mid-region complex is involved in the regulation of LFA-1 function.
Tan
S M
SM
Medical Research Council Immunochemistry Unit, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom.
Robinson
M K
MK
Drbal
K
K
van Kooyk
Y
Y
Shaw
J M
JM
Law
S K
SK
D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry; D018821:CD18 Antigens / Q000737:chemistry*; D019556:COS Cells; D002448:Cell Adhesion; D018076:DNA, Complementary / Q000378:metabolism; D000939:Epitopes; D005434:Flow Cytometry; D015723:Gene Library; D006801:Humans; D018799:Intercellular Adhesion Molecule-1 / Q000378:metabolism; D016169:Lymphocyte Function-Associated Antigen-1 / Q000378:metabolism; D008969:Molecular Sequence Data; D011233:Precipitin Tests; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D014162:Transfection
D000911:Antibodies, Monoclonal; D018821:CD18 Antigens; D018076:DNA, Complementary; D000939:Epitopes; D016169:Lymphocyte Function-Associated Antigen-1; D018799:Intercellular Adhesion Molecule-1