STRUCTURE OF THE POLYGLUTAMYL CHAIN OF TUBULIN - OCCURRENCE OF ALPHA-LINKAGE AND GAMMA-LINKAGE BETWEEN GLUTAMYL UNITS REVEALED BY MONOREACTIVE POLYCLONAL ANTIBODIES

Polyglutamylation, a posttranslational modification which consists of the sequential addition of one to six glutamyl units in the carboxy-te rminal domain of bath tubulin subunits, is a major event in neurons. I ts structure has been investigated by using monoreactive polyclonal an tibodies directed against distinct glutamylation motifs, ie alpha- and gamma-linkages between glutamyl units. It is shown that, beside alpha -linkages previously characterized, gamma-linkages also occur in gluta myl chains of brain tubulin. The co-existence of these two basic motif s leads to a conception of the polyglutamyl chain with a very sophisti cated structure which could, through its complexity, help the microtub ule to reach its structure and fulfil its functions.