PROTEIN-PROTEIN INTERACTIONS BETWEEN KERATIN POLYPEPTIDES EXPRESSED IN THE YEAST 2-HYBRID SYSTEM

Keratin filaments are obligatory heteropolymers of type I and type II keratin polypeptides. Specific type I/type II pairs are coexpressed in vivo. In contrast, all type I/type II pairs assemble into filaments i n vitro, but the different pairs have different stabilities as demonst rated by treatment with increasing concentrations of urea. We have use d the yeast two-hybrid system to analyse type If type II interactions in a cellular context. We measured interactions between two different keratin pairs and we confirm the findings that K6+K17 form very stable heterodimers whereas K8+K18 interactions were weaker. The deletion of head domains did not reduce the strength of type I/type TI interactio ns. Rather, the affinities were increased and the differences between the two pairs were retained in headless mutants. These findings argue against a major role of the head domains in directing heterodimer inte ractions and in defining heterodimer stabilities. (C) 1998 Elsevier Sc ience B.V.