ASSEMBLY OF NEMATODE CUTICLE - ROLE OF HYDROPHOBIC INTERACTIONS IN CUT-2 CROSS-LINKING

CUT-2 is a component of cuticlin, the highly cross-linked, insoluble r esidue of the cuticle of the nematode Caenorhabditis elegans. A recomb inant fragment of CUT-2, produced in E. coli, can be cross-linked in v itro by horse radish peroxidase via dityrosine formation to give large molecular species [1]. In this paper it is shown that the formation o f CUT-2 polymers is greatly favoured over that of CUT-2 oligomers as n o low molecular weight intermediates, dimers or trimers can be detecte d even when the cross-linking reaction is slowed or interrupted before completion. This suggests that recombinant CUT-2 forms large non-cova lent complexes that are the only competent substrate for cross-linking . The inhibition of cross-linking by urea and the behavior of recombin ant CUT-2 in size-exclusion chromatography under a variety of conditio ns suggest that hydrophobic interactions are important in the formatio n and stabilization of these complexes. The complexes are excellent su bstrates for cross-linking but react poorly with free tyrosine. In con trast, a soluble recombinant CUT-2 is a poor substrate for cross-linki ng but can efficiently react with free tyrosine.