Sequence requirements for formation of conformational variants of tau similar to those found in Alzheimer's disease

Alz-50 and MC-1 monoclonal antibody reactivity is dependent on both the ext reme N-terminus of tau (residues 7-9) and a 30-amino acid sequence of tau ( amino acids 312-342) in the third microtubule binding domain, suggesting th at the specificity of the Alz-50 and MC-1 antibodies for Alzheimer's diseas e (AD) pathological tau lies in their ability to recognize a specific confo rmation of the tau molecule in AD. The present study uses deletional and si te-directed mutants of tau to further refine the C-terminal (third microtub ule binding domain) epitope requirements for Alz-50, MC-1, and several new antibodies that recognize similar epitopes in tau to amino acids 313-322 of tau, and to demonstrate that intervening portions of the tau molecule are not required for the formation of conformational variants of tau similar to those seen in AD. Further analysis of deletional and site-directed mutatio ns of tau demonstrate subtle variations in the epitope requirements for Alz -50, MC-1, CP-1, CP-2, and CP-28, suggesting that these antibodies, albeit different, all recognize a similar pathological conformation of tau, Additi onal experiments using synthetic peptides demonstrate that the NH2-terminal (amino acids 1-18) and COOH-terminal (amino acids 309-326) portions of the Alz-50, MC-1, CP-1, CP-2, and CP-28 epitopes can interact with high affini ty under near physiological conditions. (C) 1999 Wiley-Liss, Inc.