Collectins--soluble proteins containing collagenous regions and lectin domains--and their roles in innate immunity.

The collectins are a group of mammalian lectins containing collagen-like regions. They include mannan binding protein, bovine conglutinin, lung surfactant protein A, lung surfactant protein D, and a newly discovered bovine protein named collectin-43. These proteins share a very similar modular domain composition and overall 3-dimensional structure. They also appear to play similar biological roles in the preimmune defense against micro-organisms in both serum and lung surfactant. The close evolutionary relationship between the collectins is further emphasized by a common pattern of exons in their genomic structures and the presence of a gene cluster on chromosome 10 in humans that contains the genes known for the human collectins. Studies on the structure/function relationships within the collectins could provide insight into the properties of a growing number of proteins also containing collagenous regions such as C1q, the hibernation protein, the alpha- and beta-ficolins, as well as the membrane acetylcholinesterase and the macrophage scavenger receptor.