Fanali Chiara, Inzitari Rosanna, Cabras Tiziana, Fiorita Antonella, Scarano Emanuele, Patamia Maria, Retruzzelli Raffaele, Bennick Anders, Messana Irene, Castagnola Massimo
Institute of Biochemistry and Clinical Biochemistry, Catholic University, Largo F. Vito, Rome, Italy.
J Sep Sci. 2008 Feb;31(3):516-22. doi: 10.1002/jssc.200700343.
Basic proline-rich proteins (bPRPs) are a class of proteins widely present in saliva of humans and other mammals. They are synthesized as preproproteins and enzymatically cleaved into small peptides before secretion from the salivary glands. Recently, we characterized two proline-rich peptides (SP-A and SP-B) in parotid secretory granules of pig (Sus Scrofa) that are derived from three isoforms of a PRP proprotein (Swiss-Prot data bank: Q95JC9-1, Q95JC9-2 and Q95JC9-3). Together the coding regions for SP-A and SP-B, which are repeated many times, account for 52-70% of the coding regions of the PRP proproteins. This study was undertaken to identify peptides encoded by unassigned regions of the PRP proproteins. RP-HPLC-ESI-IT-MS analysis of enriched granule preparations from pig parotid glands by two different analytical strategies identified ten new proline-rich peptides derived from the three proproteins. Together with the coding regions for SP-A and SP-B already identified it was possible to assign 68-75% of the proproteins coding regions. The peptide sequences indicated a number of unusual proteolytic cleavage sites suggesting the presence of unknown proprotein convertases.
富含脯氨酸的基础蛋白（bPRPs）是一类广泛存在于人类和其他哺乳动物唾液中的蛋白质。它们最初作为前体蛋白被合成，在从唾液腺分泌之前经酶切作用裂解为小肽。最近，我们鉴定了猪（Sus Scrofa）腮腺分泌颗粒中的两种富含脯氨酸的肽（SP-A和SP-B），它们来源于一种PRP前体蛋白的三种同工型（瑞士蛋白质数据库：Q95JC9-1、Q95JC9-2和Q95JC9-3）。SP-A和SP-B的编码区域多次重复，它们共同占PRP前体蛋白编码区域的52 - 70%。本研究旨在鉴定PRP前体蛋白未分配区域所编码的肽。通过两种不同的分析策略，对猪腮腺富含颗粒制剂进行RP-HPLC-ESI-IT-MS分析，鉴定出了十种源自这三种前体蛋白的新的富含脯氨酸的肽。连同已鉴定的SP-A和SP-B的编码区域，有可能确定前体蛋白编码区域的68 - 75%。肽序列显示了许多不寻常的蛋白水解切割位点，这表明存在未知的前体蛋白转化酶。
