Collectins are part of the innate immune system as they bind nonself
glycoconjugates on the surface of microorganisms and inhibit
infection by direct neutralization, agglutination or opsonization of the invaders.
Conglutinin and
CL-43 are
serum proteins that have only been found and characterized in Bovidae. We have studied molecular and genomic characteristics of
CL-43 to identify polymorphisms that might be associated with disease-susceptible phenotypes or other traits in cattle, and to elucidate how the Bovidae may benefit from possessing additional
collectins. Screening a bovine cDNA library resulted in the isolation of two plasmid clones that encoded the entire translated sequence of
CL-43. The 5'-untranslated end and start point of transcription were identified by 5'-RACE and showed that the
mRNA transcript comprises either 1326 or 1241
nucleotides because of alternative splicing. Both transcripts encode a
protein of 321
amino acids including a
signal peptide of 20 residues. Characterization of two overlapping genomic lambda phage clones showed that the gene comprised seven exons spanning 8.5 kbp. The
CL-43 gene, like the
conglutinin gene, was mapped to Bos taurus chromosome 28 at q1.8. The
CL-43 promoter has 96% identity with the
conglutinin promoter recently described by us, and the assignment of potential cis-regulatory elements shows that several hepatic
transcription factors may regulate transcription in the
acute phase response and in response to metabolic changes.