Effect of Cysteine 85 on Biochemical Properties and Biological Function of Human Surfactant Protein A Variants

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• 作者：Guirong Wang ; Catherine Myers ; Anatoly Mikerov ; Joanna Floros
• 刊名：Biochemistry
• 出版年：2007
• 出版时间：July 17, 2007
• 年：2007
• 卷：46
• 期：28
• 页码：8425 - 8435
• 全文大小：480K
• 年卷期：v.46,no.28(July 17, 2007)
• ISSN：1520-4995

文摘

Four "core" amino acid differences within the collagen-like domain distinguish the humansurfactant protein A1 (SP-A1) variants from the SP-A2 variants. One of these, cysteine 85 that couldform intermolecular disulfide bonds, is present in SP-A1 (Cys⁸⁵) and absent in SP-A2 (Arg⁸⁵). Wehypothesized that residue 85 affects both the structure and function of SP-A1 and SP-A2 variants. To testthis, wild-type (WT) variants, 6A² of SP-A1 and 1A⁰ of SP-A2, and their mutants (6A^2(C85R) and 1A^0(R85C))were generated and studied. We found the following: (1) Residue 85 affected the binding ability to mannoseand the oligomerization pattern of SP-As. The 1A^0(R85C) and 6A^2(C85R) patterns were similar and/or resembledthose of WT 6A² and 1A⁰, respectively. (2) Both SP-A WT and mutants differentially induced rough LPSand Pseudomonas aeruginosa aggregation in the following order: 1A⁰ > 6A² > 6A^2(C85R) > 1A^0(R85C) forRe-LPS aggregation and 1A⁰ > 6A² = 6A^2(C85R) = 1A^0(R85C) for bacterial aggregation. (3) SP-A WT andmutants enhanced phagocytosis of P. aeruginosa by rat alveolar macrophages. Their phagocytic indexorder was 6A^2(C85R) > 1A⁰ > 6A² = 1A^0(R85C). The activity of mutant 1A^0(C85R) was significantly lowerthan WT 1A⁰ but similar to 6A². Compared to WT 6A², the 6A^2(C85R) mutant exhibited a significantlyhigher activity. These results indicate that the SP-A variant/mutant with Arg⁸⁵ exhibits a higher ability toenhance bacterial phagocytosis than that with Cys⁸⁵. Residue 85 plays an important role in the structureand function of SP-A and is a major factor for the differences between SP-A1 and SP-A2 variants.