Open AccessBinding to human dipeptidyl peptidase IV by adenosine deaminase and antibodies that inhibit ligand binding involves overlapping, discontinuous sites on a predicted β propeller domain
Author(s) -
Abbott Catherine A.,
McCaughan Geoffrey W.,
Levy Miriam T.,
Church W. Bret,
Gorrell Mark D.
Publication year - 1999
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1046/j.1432-1327.1999.00902.x
Subject(s) - dipeptidyl peptidase , dipeptidyl peptidase 4 , adenosine deaminase , biochemistry , microbiology and biotechnology , amino acid , binding site , monoclonal antibody , serine protease , chemistry , antibody , binding domain , point mutation , biology , enzyme , protease , mutation , gene , type 2 diabetes , immunology , diabetes mellitus , endocrinology
Dipeptidyl peptidase IV (DPPIV) is an atypical serine protease that modifies the biological activities of certain chemokines and neuropeptides. In addition, human DPPIV, also known as the T‐cell activation antigen CD26, binds adenosine deaminase (ADA) to the T‐cell surface, thus protecting the T‐cell from adenosine‐mediated inhibition of proliferation. Mutations were engineered into DPPIV (five point, 16 single point and six deletion mutations) to examine the binding of ADA and 19 monoclonal antibodies. Deletions of C‐terminal residues from the 738‐residue extracellular portion of DPPIV showed that the 214 residues C‐terminal to Ser552 were not required for ADA binding and that peptidase activity could be ablated by deletion of 20 residues from the C‐terminus. Point mutations at either of two locations, Leu294 and Val341, ablated ADA binding. Binding by six anti‐DPPIV antibodies that inhibited ADA binding was found to require Leu340 to Arg343 and Thr440/Lys441 but not the 214 residues C‐terminal to Ser552. The 13 other antibodies studied bound to a truncated DPPIV consisting of amino acids 1–356. Therefore, the binding sites on DPPIV of ADA and antibodies that inhibit ADA binding are discontinuous and overlapping. Moreover, the 47 and 97 residue spacing of amino acids in these binding sites concords with their location on a β propeller fold consisting of repeated β sheets of about 50 amino acids.