Structural analysis of sulphated glycoprotein 2 from amino acid sequence. Relationship to clusterin and serum protein 40,40.
Sulphated glycoprotein 2 (SGP-2) is the major secreted protein product of rat Sertoli cells; likewise, clusterin is a major constituent of ram rete testis fluid. Isolation and sequencing of the intact subunits and peptides derived from clusterin show that it is the ram homologue of rat SGP-2. Human serum protein 40,40 (SP-40,40), a component of the SC5b-9 complex of complement, has recently been reported to be the human homologue of rat SGP-2. Analysis of the amino acid sequences of rat SGP-2 and human SP-40,40 show that both of these proteins have a significant relationship to the heavy chain of myosin. The regions of highest sequence similarity correspond to the major amphipathic domains in SGP-2/SP-40,40 and the long alpha-helical-tail domain of myosin, which forms a rod-like structure. SGP-2 has anomalous sedimentation behaviour which indicates that it probably exists in an extended conformation. A putative dinucleotide-binding structure has been identified in the longest stretch of identity between SGP-2 and SP-40,40. Elucidation of these features of SGP-2 and SP-40,40 may help to direct future studies into the role of these proteins in the reproductive and complement systems.
Tsuruta
J K
JK
Biochemistry/Biophysics Program, Washington State University, Pullman 99164-4660.
Wong
K
K
Fritz
I B
IB
Griswold
M D
MD
D000595:Amino Acid Sequence; D000818:Animals; D001798:Blood Proteins / Q000032:analysis*; D002851:Chromatography, High Pressure Liquid; D051152:Clusterin; D006023:Glycoproteins / Q000032:analysis* / Q000302:isolation & purification; D006801:Humans; D008297:Male; D008958:Models, Molecular; D018832:Molecular Chaperones; D008969:Molecular Sequence Data; D015879:Myosin Subfragments / Q000032:analysis; D011487:Protein Conformation; D051381:Rats; D012756:Sheep; D013045:Species Specificity; D013737:Testis / Q000032:analysis*
D001798:Blood Proteins; C495242:CLU protein, human; D051152:Clusterin; D006023:Glycoproteins; D018832:Molecular Chaperones; D015879:Myosin Subfragments