Ravindranath Rajeswari M H, Basilrose Rajam M, Ravindranath Naren H, Vaitheesvaran Bhavapriya
Center for Craniofacial Molecular Biology, School of Dentistry, University of Southern California, Los Angeles 90033-1004, USA.
J Biol Chem. 2003 May 30;278(22):20293-302. doi: 10.1074/jbc.M211184200. Epub 2003 Mar 25.
The enamel protein amelogenin binds to GlcNAc (Ravindranath, R. M. H., Moradian-Oldak, R., and Fincham, A.G. (1999) J. Biol. Chem. 274, 2464-2471) and to the GlcNAc-mimicking peptide (GMp) (Ravindranath, R. M. H., Tam, W., Nguyen, P., and Fincham, A. G. (2000) J. Biol. Chem. 275, 39654-39661). The GMp motif in the N-terminal region of the cytokeratin 14 of ameloblasts binds to trityrosyl motif peptide (ATMP) of amelogenin (Ravindranath, R. M. H., Tam, W., Bringas, P., Santos, V., and Fincham, A. G. (2001) J. Biol. Chem. 276, 36586 - 36597). K14 (Type I) pairs with K5 (Type II) in basal epithelial cells; GlcNAc-acylated K5 is identified in ameloblasts. Dosimetric analysis showed the binding affinity of amelogenin to K5 and to GlcNAc-acylated-positive control, ovalbumin. The specific binding of [3H]ATMP with K5 or ovalbumin was confirmed by Scatchard analysis. [3H]ATMP failed to bind to K5 after removal of GlcNAc. Blocking K5 with ATMP abrogates the K5-amelogenin interaction. K5 failed to bind to ATMP when the third proline was substituted with threonine, as in some cases of human X-linked amelogenesis imperfecta or when tyrosyl residues were substituted with phenylalanine. Confocal laser scan microscopic observations on ameloblasts during postnatal (PN) growth of the teeth showed that the K5-amelogenin complex migrated from the cytoplasm to the periphery (on PN day 1) and accumulated at the apical region on day 3. Secretion of amelogenin commences from day 1. K5, similar to K14, may play a role of chaperone during secretion of amelogenin. Upon secretion of amelogenin, K5 pairs with K14. Pairing of K5 and K14 commences on day 3 and ends on day 9. The pairing of K5 and K14 marks the end of secretion of amelogenin.
釉质蛋白牙釉蛋白与N-乙酰葡糖胺结合（拉温德拉纳特，R.M.H.，莫拉迪安 - 奥尔达克，R.，和芬奇姆，A.G.（1999年）《生物化学杂志》274卷，2464 - 2471页），也与模拟N-乙酰葡糖胺的肽（GMp）结合（拉温德拉纳特，R.M.H.，谭，W.，阮，P.，和芬奇姆，A.G.（2000年）《生物化学杂志》275卷，39654 - 39661页）。成釉细胞细胞角蛋白14 N端区域的GMp基序与牙釉蛋白的三酪氨酸基序肽（ATMP）结合（拉温德拉纳特，R.M.H.，谭，W.，布林加斯，P.，桑托斯，V.，和芬奇姆，A.G.（2001年）《生物化学杂志》276卷，36586 - 36597页）。在基底上皮细胞中，K14（I型）与K5（II型）配对；在成釉细胞中鉴定出N-乙酰葡糖胺酰化的K5。剂量分析显示了牙釉蛋白与K5以及与N-乙酰葡糖胺酰化阳性对照卵清蛋白的结合亲和力。通过斯卡查德分析证实了[³H]ATMP与K5或卵清蛋白的特异性结合。去除N-乙酰葡糖胺后，[³H]ATMP无法与K5结合。用ATMP阻断K5可消除K5与牙釉蛋白的相互作用。当第三个脯氨酸被苏氨酸取代时，如在某些人类X连锁釉质发育不全病例中或酪氨酸残基被苯丙氨酸取代时，K5无法与ATMP结合。对出生后（PN）牙齿生长过程中成釉细胞的共聚焦激光扫描显微镜观察表明，K5 - 牙釉蛋白复合物从细胞质迁移到外周（PN第1天），并在第3天积聚在顶端区域。牙釉蛋白的分泌从第1天开始。K5与K14类似，可能在牙釉蛋白分泌过程中起伴侣作用。牙釉蛋白分泌后，K5与K14配对。K5和K14的配对在第3天开始，在第9天结束。K5和K14的配对标志着牙釉蛋白分泌的结束。
