Mouse surfactant protein-D. cDNA cloning, characterization, and gene localization to chromosome 14
Motwani, M.; White, R.A.; Guo, N.; Dowler, L.L.; Tauber, A.I.; Sastry, K.N.
Journal of Immunology 155(12): 5671-5677
1995
ISSN/ISBN: 0022-1767 PMID: 7499852 Document Number: 441224
Surfactant protein-D (SP-D) is a collectin associated with surfactant in the lung. It acts as an opsonin for diverse microorganisms and a chemoattractant for phagocytic cells. To determine the structure of mouse SP-D, clones from a B6/CBAF1J strain lung cDNA library were isolated and characterized using a polymerase chain reaction (PCR)-derived genomic probe. The deduced sequence predicted a 19-amino acid signal sequence, a 25-amino acid long NH2 terminus with 2 cysteines, followed by an uninterrupted collagen domain with 59 Gly-X-Y repeats. Next, a short 'neck' domain of 28 amino acids, with the potential to form trimeric alpha -helical coiled coil, was found, ending in a COOH-terminal 125-amino acid carbohydrate recognition domain. The mature mouse SP-D protein of 355 amino acids showed strong homology to rat (92% identity), human (76%) and cattle (72%) SP-D amino acid sequences. Northern blot and reverse transcriptase-PCR analysis revealed that the mouse SP-D gene was expressed predominantly in the lungs, heart, stomach and kidneys, but not in the brain. In contrast, mouse surfactant protein-A (SP-A) mRNA expression was restricted to the lungs. Human lung and stomach, but not heart or liver, were found to express SP-D mRNA, was determined by PCR. The mouse SP-D gene (Sftp4) was mapped to chromosome 14, closely linked to the genes for other collagenous lectins, mannose-binding protein-A (Mbl1) and SP-A (Sftp1).