Role of crosslinking in fiber formation

The synthesis of elastin by smooth muscle cells is demostrated by amino acid analyses and the presence of lysine-derived crosslinks. The data reveal that the ratio of allysine to aldol decreases with time in culture. The presence of insoluble elastin correlates well with the presence of the reduced aldol condensate in these cells. If the formation of the desmosines occurs by the condensation of the aldol and dehyrolysinonorleucine, the presence of the latter may be rate-limiting since the cells display little or no dehydrolysinonorleucine. Several peptides containing the desmosine crosslink were purified and partially sequenced. The data indicate that desmosines crosslink two polypeptide chains and that both desmosine and isodesmosine are present in the same primary sequence approximately equally substituted. A possible role for tyrosine in the regulation of desmosine formation is presented.