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FDC-SP or follicular dendritic cell-secreted protein, is a small, secreted protein, located on chromosome 4 in humans. It is thought to play an immune role in the junctional epithelium at the gingival crevice in the human mouth. It is very similar in structure to statherin, a protein contained in saliva. 〔 〕 ==Structure and genetics== FDC-SP is an 68-amino acid protein containing a signal peptide at its N terminus, which is used for directing the transport of the protein. Adjacent to the signal peptide, the protein contains a highly-charged N-terminal sequence.〔 The C-terminal half of FDC-SP is proline-rich and not highly conserved between species, but the alignment of proline residues within this region is highly conserved. FDC-SP homologues are only easily located within the human, rat, mouse and chimpanzee genome. There is a 70% sequence homology between mouse and rat and a 45% homology between human and mouse. The N-terminal, however, is highly conserved between all three species and is thought to contain potential casein kinase 2 (CK2) phosphorylation sites. CK2 is a constitutively and widely expressed serine/threonine kinase that has many substrates related to signal transduction and cell growth regulation. Several casein genes have also been found nearby to the FDC-SP gene. Numerous genes that are expressed in oral tissues, including statherin, mucin, ameloblastin, histatin, enamelin and proline-rich protein are also located in close proximity to the FDC-SP gene. This indicates that the aforementioned genes may be expressed through the same mechanism. The recent evolutionary development of FDC-SP correlates with the development of certain aspects of the mammalian immune system and with the emergence of the follicular germinal centre (GC) reaction in secondary lymphoid tissues.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「FDC-SP」の詳細全文を読む スポンサード リンク
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