Molecular genetical and phylogenic studies on human salivary proline-rich protein P-B.

用PCR方法克隆了人唾液富含脯氨酸蛋白P-B的编码基因。分离的克隆被命名为PBII，并测定了PBII的核苷酸序列（登录号AB 031740）。PBII是AT富集基因，具有3个外显子。它与我以前克隆的-PBI具有高度的序列同源性。两个基因在整个分子范围内具有同源性。两个基因的外显子2完全相同。PBII的内含子2长度比PBI长600 bp。尽管PBII的第3外显子比FBI长，|PBII的基因产物（p-B）比PBI的推定基因产物（P-B1）短55个残基，这主要是由于PBI的终止密码子向3'方向移动。用Stan福特G3辐射杂交作图板和PBII基因的引物，将PBII基因定位在4号染色体长臂上，靠近statherin、histatin、PBI和tear proline rich protein的位置。牛的牙胚和牙髓。牛作为实验材料，因为牛发育中的釉质中含有P-B样蛋白。从PCR结果来看，牛的颌下腺、牙胚和牙髓是合成P-B或P-B样蛋白的组织，随着研究组织数量的增加，有可能根据P-B合成组织的共同特征来推测P-B的生理功能。

The gene encoding human salivary proline-rich protein P-B was cloned by PCR. The clone isolated was named PBII and the nucleotide sequence of PBII was determined (accession number AB031740). PBII is the AT rich gene and has 3 exons. it has high degree of sequence homology with-PBI which I cloned previously. Two genes have homology over the entire range of molecules. Exons 2 of two genes are completely identical. Homology of the middle part of each molecule was relatively low and the length of intron 2 of PBII was longer than that of PBI by 6OObp. In spite that exon 3 of PBII was longer than that of FBI, |the gene product of PBII (p-B) is shorter than the putative gene product (P-Bl) of PBI by 55 residues, mainly because of the shift of stop codon of PBI to 3' direction. Though PBII and PBI belong to the same gene family, only PBII isconsidered to be transcribed in human submaxillary gland.PBII gene was mapped on long arm of chromosome 4 near statherin, histatin, PBI and tear proline rich protein, by PCR using Stan ford G3 radiation hybrid mapping panel and primers derived from PBII.To determine synthesis site of P-B or P-B like protein, mRNAs were prepared from submaxillary gland, tooth germ and tooth pulp of Bos taurus. Bos taurus was chosen as experimental material since bovine developing enamel is known to contain P-B like protein. Judging from PCR results, submaxillary gland, tooth germ and tooth pulp of Bos taurus are considered to be the tissues synthesizing P-B or P-B like protein, increasing numbers of tissues studied will make it possible to estimate the physiological functions of P-B based on the common features of P-B synthesizing-tissues.