Structure and expression of the gene encoding cystatin D, a novel human cysteine proteinase inhibitor.
A new member of the human cystatin multigene family has been cloned from a genomic library using a cystatin C cDNA probe. The complete nucleotide sequence of a 4.3-kilobase DNA segment, containing a complete gene with structure very similar to those of known Family 2 cystatin genes, was determined. The novel gene, called CST4, is composed of three exons and two introns. It contains the coding information for a protein of 142 amino acid residues, which has been tentatively called cystatin D. The deduced amino acid sequence includes a putative signal peptide and presents 51-55% identical residues with the sequences of either cystatin C or the secretory gland cystatins S, SN, or SA. The cystatin D sequence contains all regions of relevance for cysteine proteinase inhibitory activity and also the 4 cysteine residues that form disulfide bridges in the other members of cystatin Family 2. Northern blot analysis revealed that the cystatin D gene is expressed in parotid gland but not in seminal vesicle, prostate, epididymis, testis, ovary, placenta, thyroid, gastric corpus, small intestine, liver, or gall-bladder tissue. This tissue-restricted expression is in marked contrast with the wider distribution of all the other Family 2 cystatins, since cystatin C is expressed in all these tissues and the secretory gland cystatins are present in saliva, seminal plasma, and tears. Cystatin D, being the first described member of a third subfamily within the cystatin Family 2, thus appears to have a distinct function in the body in contrast to other cystatins.
Departamento de Biologia Funcional, Universidad de Oviedo, Spain.
J P
JP
Freije
M
M
Abrahamson
I
I
Olafsson
G
G
Velasco
A
A
Grubb
C
C
López-Otín
D000595:Amino Acid Sequence; D001483:Base Sequence; D015152:Blotting, Northern; D015139:Blotting, Southern; D003001:Cloning, Molecular; D015891:Cystatins / Q000235:genetics*; D015853:Cysteine Proteinase Inhibitors / Q000235:genetics*; D004247:DNA / Q000235:genetics; D015870:Gene Expression; D006801:Humans; D008969:Molecular Sequence Data; D005810:Multigene Family; D015183:Restriction Mapping
D015891:Cystatins; D015853:Cysteine Proteinase Inhibitors; C071378:CST5 protein, human; D004247:DNA