蛋白质A

现有可用的蛋白结构：
PDB	1dee, 1l6x

Protein A
Protein A
	Structure of a domain of protein A as a three-helix bundle binding to the heavy variable chain of a VH3 human Fab left. Minimized protein A bound to Fc fragment of Rituximab.
鉴定
标志	SpA
SCOP（英语：Structural Classification of Proteins）	1DEE / SUPFAM
PDB
现有可用的蛋白结构：
PDB	1dee, 1l6x

蛋白质A（英语：Protein A）为金黄色葡萄球菌表面上发现的一种表面蛋白，大小约为42 kDa。该蛋白由 spa 基因转译而成，并由DNA的拓朴结构、包内渗透压，以及一个名为ArlS-ArlR的双单元调控系统（英语：two-component regulatory system）调控。该蛋白可以与免疫球蛋白结合，故常用于生化研究。该蛋白三维构造中有五个同源性免疫球蛋白结合域，每个结合域都能与多种哺乳类的免疫球蛋白结合，最主要为IgG。蛋白质A能与大多数免疫球蛋白重链的Fc区域（英语：Fc region）结合，甚至可与人类VH3蛋白质家族的Fab区域（英语：Fab region）结合。当蛋白质A与免疫球蛋白结合后，这些免疫球蛋白便失去了作用，进而摧毁免疫系统的吞噬作用及调理作用（英语：opsonization）。

参考文献

^ Graille M, Stura EA, Corper AL, Sutton BJ, Taussig MJ, Charbonnier JB, Silverman GJ. Crystal structure of a Staphylococcus aureus protein A domain complexed with the Fab fragment of a human IgM antibody: structural basis for recognition of B-cell receptors and superantigen activity. Proceedings of the National Academy of Sciences of the United States of America. May 2000, 97 (10): 5399–404. PMC 25840  . PMID 10805799. doi:10.1073/pnas.97.10.5399.
^ Idusogie EE, Presta LG, Gazzano-Santoro H, Totpal K, Wong PY, Ultsch M, Meng YG, Mulkerrin MG. Mapping of the C1q binding site on rituxan, a chimeric antibody with a human IgG1 Fc. Journal of Immunology. April 2000, 164 (8): 4178–84. PMID 10754313. doi:10.4049/jimmunol.164.8.4178.

[pmid10805799-1] Graille M, Stura EA, Corper AL, Sutton BJ, Taussig MJ, Charbonnier JB, Silverman GJ. Crystal structure of a Staphylococcus aureus protein A domain complexed with the Fab fragment of a human IgM antibody: structural basis for recognition of B-cell receptors and superantigen activity. Proceedings of the National Academy of Sciences of the United States of America. May 2000, 97 (10): 5399–404. PMC 25840  . PMID 10805799. doi:10.1073/pnas.97.10.5399.

[pmid10754313-2] Idusogie EE, Presta LG, Gazzano-Santoro H, Totpal K, Wong PY, Ultsch M, Meng YG, Mulkerrin MG. Mapping of the C1q binding site on rituxan, a chimeric antibody with a human IgG1 Fc. Journal of Immunology. April 2000, 164 (8): 4178–84. PMID 10754313. doi:10.4049/jimmunol.164.8.4178.

[1]

[2]