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A novel cDNA has been isolated from pig parotid glands by 3' and 5' rapid amplification of cDNA ends and designated parotid secretory protein (PSP). The open reading frame of this cDNA covers 714 bases, encoding 238 amino acids, which show 56% identity with human PSP at the level of the primary protein structure. The PSP genomic sequence comprises eight exons and seven introns, is approximately 22 kb in size, determined by sequencing, and maps to pig chromosome 17q21-q23. RT-PCR, dot blot, and Northern blot analyses demonstrated that PSP is strongly expressed in parotid glands, but is not present in heart, liver, lung, kidney, muscle, or stomach. A search for functionally significant protein motifs revealed consensus sequences for casein kinase II phosphorylation and N-myristoylation. We observed a unique amino acid sequence pattern consisting of the residues Leu-X(6)-Leu-X(6)-Leu-X(7)-Leu-X(6)-Leu-X(6)-Leu near the amino-terminal portion of the protein, which is similar to the leucine zipper.

With ESTs from porcine fatty tissue and cDNA sequences from human, bovine and mouse in non-reduncdant database and dbEST in GenBank,we sampled cDNA sequences of 70 function-known genes in four species on the base of randomly sampling method, analyzed the mutation pattern of 70 x 150 bp linking sequences between them, and established an integrated phylogenic analysis method. The results showed that 391 single bases mutations were found in 70 x 150 bp linking sequences alignment among four species. The number of mutation bases between them were greatly exceeded the 1/1000 predicted in the human genome analysis. C/T(T/C) and A/G (G/A) transitions were the major types of single base mutation. The genetic relationship between pig and bovine who are both Artiodactylous is the nearest, the next is human, and the farthest is mouse. The differentiation sequence taken place in four species from the same ancestor is that mouse is the earliest one, and the latter human, and pig and bovine are the latest.