Structural and biological characteristics of connective tissue activating peptide (CTAP-III), a major human platelet-derived growth factor.
Connective tissue activating peptides (CTAPs) extracted from leukocytes and platelets stimulate glycolysis and synthesis of glycosaminoglycan and DNA in cultured human connective tissue cells. CTAP-III, isolated from fresh or outdated human platelets, is a low molecular weight single-chain protein with an isoelectric point of 8.5 that markedly stimulates DNA synthesis and multiple aspects of glycosaminoglycan and proteoglycan metabolism. This report presents a definitive comparison of CTAP-III prepared by two methods [one designated (A), alternative] with similar platelet proteins described by others, beta-thromboglobulin (beta-TG) and low-affinity platelet factor 4 (LA-PF-4). CTAP-III, CTAP-III(A), LA-PF-4, and beta-TG have common antigenic determinants documented by immunoprecipitation and radioimmunoassay. CTAP-III, CTAP-III(A), and LA-PF-4 are biologically active in that they stimulate DNA and glycosaminoglycan synthesis by human synovial cells; beta-TG is inactive. Carboxyl-terminal digestion gave identical terminal sequences for CTAP-III, CTAP-III(A), and beta-TG. Amino-terminal sequence data indicate that CTAP-III and CTAP-III(A) (also LA-PF-4) are identical and differ from beta-TG only by an additional amino-terminal tetrapeptide (Asn-Leu-Ala-Lys-). The biologically active molecule, CTAP-III, may be proteolytically converted to its inactive degradation product (beta-TG) in the course of platelet aging, platelet storage, release from the platelets, or initiation of biological activity.
D000595:Amino Acid Sequence; D001792:Blood Platelets / Q000032:analysis*; D002455:Cell Division / Q000187:drug effects; D003239:Connective Tissue Cells; D004247:DNA / Q000096:biosynthesis; D006025:Glycosaminoglycans / Q000096:biosynthesis; D006133:Growth Substances / Q000302:isolation & purification*; D006801:Humans; D010446:Peptide Fragments / Q000032:analysis; D010455:Peptides / Q000302:isolation & purification*; D010982:Platelet-Derived Growth Factor
D006025:Glycosaminoglycans; D006133:Growth Substances; D010446:Peptide Fragments; D010455:Peptides; D010982:Platelet-Derived Growth Factor; D004247:DNA