Papilins are homologous, secreted extracellular matrix proteins which share a 
common order of protein domains. They occur widely, from nematodes to man, and 
can differ in the number of repeats of a given type of domain. Within one 
species the number of repeats can vary by differential RNA splicing. A 
distinctly conserved cassette of domains at the amino-end of papilins is 
homologous with a cassette of protein domains at the carboxyl-end of the ADAMTS 
subgroup of secreted, matrix-associated metalloproteases. Papilins primarily 
occur in basement membranes. Papilins interact with several extracellular matrix 
components and ADAMTS enzymes. Papilins are essential for embryonic development 
of Drosophila melanogaster and Caenorhabditis elegans.