Clements S, Mehansho H, Carlson D M
J Biol Chem. 1985 Nov 5;260(25):13471-7.
Multigene families encode the proline-rich proteins that are so prominent in human saliva and are dramatically induced in mouse and rat salivary glands by isoproterenol treatment and by feeding tannins. A cDNA encoding an acidic proline-rich protein of rat has been sequenced (Ziemer, M. A., Swain, W. F., Rutter, W. J., Clements, S., Ann, D. K., and Carlson D. M. (1984) J. Biol. Chem. 259, 10475-10480). This study presents the nucleotide sequences of five additional proline-rich protein cDNAs complementary to both mouse and rat parotid and submandibular gland mRNAs. Amino acid compositions deduced from the nucleotide sequences are typical for proline-rich proteins: 25-45% proline, 18-22% glycine, and 18-22% glutamine and generally an absence of sulfur-containing amino acids except for the initiator methionine. These proline-rich proteins display unusual repeating peptide sequences of 14-19 amino acids. The derived amino acid sequence of the cDNA insert of plasmid pMP1 from mouse has a 19-amino acid sequence which is repeated four times. The inserts of plasmids pUMP40 and pUMP4 also from mouse encode for 12 and 11 repeats of a 14-amino acid peptide, respectively. These repetitive sequences, and others from rat and mouse cDNAs and from human genomic clones, all show very high homologies and likely evolved from duplication of internal portions of an ancestral gene. Gene conversion could account for the high degree of conservation of nucleotide sequences of the repeat regions. Protein derived from the nucleotide sequences are all characterized by four general regions: a putative signal peptide, a transition region, the repetitive region, and a carboxyl-terminal region. The 5'-flanking sequences and sequences encoding the putative signal peptides are highly conserved (greater than 94%) in all six cDNAs. This sequence conservation may be important in the regulation of the biosynthesis of these unusual proteins.
多基因家族编码富含脯氨酸的蛋白质，这些蛋白质在人类唾液中非常突出，并且在小鼠和大鼠的唾液腺中，通过异丙肾上腺素处理以及喂食单宁酸会显著诱导其产生。已对编码大鼠酸性富含脯氨酸蛋白质的cDNA进行了测序（齐默尔，M. A.，斯温，W. F.，鲁特，W. J.，克莱门茨，S.，安，D. K.，以及卡尔森，D. M.（1984年）《生物化学杂志》259卷，10475 - 10480页）。本研究展示了另外五个与小鼠和大鼠腮腺及颌下腺mRNA互补的富含脯氨酸蛋白质cDNA的核苷酸序列。从核苷酸序列推导的氨基酸组成是富含脯氨酸蛋白质的典型特征：脯氨酸占25 - 45%，甘氨酸占18 - 22%，谷氨酰胺占18 - 22%，并且除起始甲硫氨酸外通常不含含硫氨基酸。这些富含脯氨酸的蛋白质呈现出14 - 19个氨基酸的不寻常重复肽序列。来自小鼠的质粒pMP1的cDNA插入片段的推导氨基酸序列有一个19个氨基酸的序列，重复了四次。同样来自小鼠的质粒pUMP40和pUMP4的插入片段分别编码12个和11个14个氨基酸肽的重复序列。这些重复序列，以及来自大鼠和小鼠cDNA以及人类基因组克隆的其他序列，都显示出非常高的同源性，并且可能是由一个祖先基因内部部分的复制进化而来。基因转换可以解释重复区域核苷酸序列的高度保守性。从核苷酸序列推导的蛋白质都具有四个一般区域的特征：一个假定的信号肽、一个过渡区域、重复区域和一个羧基末端区域。在所有六个cDNA中，5'侧翼序列和编码假定信号肽的序列高度保守（大于94%）。这种序列保守性可能在这些不寻常蛋白质的生物合成调控中很重要。
