Download MendeleyCrystal structure of trimeric carbohydrate recognition and neck domains of surfactant protein A
Head, J.F., Mealy, T.R., McCormack, F.X., Seaton, B.A.(2003) J Biol Chem 278: 43254-43260
- PubMed: 12913002
- DOI: https://doi.org/10.1074/jbc.M305628200
- Primary Citation of Related Structures:
1R13, 1R14 - PubMed Abstract:
Surfactant protein A (SP-A), one of four proteins associated with pulmonary surfactant, binds with high affinity to alveolar phospholipid membranes, positioning the protein at the first line of defense against inhaled pathogens. SP-A exhibits both calcium-dependent carbohydrate binding, a characteristic of the collectin family, and specific interactions with lipid membrane components. The crystal structure of the trimeric carbohydrate recognition domain and neck domain of SP-A was solved to 2.1-A resolution with multiwavelength anomalous dispersion phasing from samarium. Two metal binding sites were identified, one in the highly conserved lectin site and the other 8.5 A away. The interdomain carbohydrate recognition domain-neck angle is significantly less in SP-A than in the homologous collectins, surfactant protein D, and mannose-binding protein. This conformational difference may endow the SP-A trimer with a more extensive hydrophobic surface capable of binding lipophilic membrane components. The appearance of this surface suggests a putative binding region for membrane-derived SP-A ligands such as phosphatidylcholine and lipid A, the endotoxic lipid component of bacterial lipopolysaccharide that mediates the potentially lethal effects of Gram-negative bacterial infection.
Organizational Affiliation:
Department of Physiology and Biophysics, Boston University School of Medicine, Boston, Massachusetts 02118, USA.
