Homology of the precursor of pulmonary surfactant-associated protein SP-B with prosaposin and sulfated glycoprotein 1.
The precursor of pulmonary surfactant-associated protein, SP-B, is composed of an NH2-terminal domain of 30 residues (a-type domain) and three tandem repeats of about 90 residues (b-type domain); biophysically active mature SP-B corresponds to the second b-type repeat. Consensus sequences constructed for the b-type repeats were used to search the data base for homologous sequences, and the search has revealed that prosaposin and sulfated glycoprotein 1 show a remarkable homology with these repeats. The domain organizations of the latter proteins, however, differ from that of SP-B precursor inasmuch as they contain four tandem copies of the b-type domain and a-type domains are present both in the NH2-terminal and COOH-terminal parts of the proteins. The implications of the homology of saposins and SP-B for their structure and function are discussed.
Patthy
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Institute of Enzymology, Hungarian Academy of Sciences, Hungary.
D000595:Amino Acid Sequence; D000818:Animals; D004285:Dogs; D006023:Glycoproteins / Q000235:genetics*; D006801:Humans; D008969:Molecular Sequence Data; D011498:Protein Precursors / Q000235:genetics*; D011510:Proteolipids / Q000235:genetics*; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants / Q000235:genetics*; D011817:Rabbits; D051381:Rats; D012091:Repetitive Sequences, Nucleic Acid; D049231:Saposins; D012689:Sequence Homology, Nucleic Acid; D013552:Swine
D006023:Glycoproteins; C483345:PSAP protein, human; D011498:Protein Precursors; D011510:Proteolipids; C483347:Psap protein, rat; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants; D049231:Saposins; C105511:surfactant protein B propeptide