Structure
Surfactant protein A (SP-A) is a protein of 248 amino acids usually found in large oligomeric structures. The mature SP-A1 monomer is a 35kDa protein that differs from SP-A2 in four amino acids at the coding region. The structure of SP-A1 monomers consists of four domains: an N-terminal, a collagen-like domain, a neck region, and a carbohydrate recognition domain. The C-terminal carbohydrate recognition domain (CRD) allows binding to various types of microorganisms and molecules. The amino acid differences that distinguish between SP-A1 and SP-A2 genes and between their corresponding variants are located at the collagen-like domain. The amino acid differences that distinguish among SFTPA1 variants are located both at the carbohydrate recognition and the collagen-like domains.
SP-A1 monomers group with other SP-A1 or SP-A2 monomers in trimeric structural subunits of 105kDa. Six of these structures group in 630 kDa structures that resemble flower bouquets. These oligomers contain a total of eighteen SP-A1 and/or SP-A2 monomers.
Read more about this topic: Pulmonary Surfactant-associated Protein A1
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