title: Heterogeneity in the collagens extracted from human embryonic calvaria.
abstract: Collagens were obtained from decalcified human embryonic calvaria by pepsin digestion. After removal of the type I collagen, the more soluble collagens were precipitated at 1.2 M NaCl (acid pH), followed by a selective precipitation step at neutral pH, using a NaCl concentration of 4.5 M. Analysis of this latter precipitate by polyacrylamide slab gel electrophoresis and ion-exchange chromatography revealed the presence of a heterogeneous group of proteins ranging in size from approximately 10 000 daltons to over 120 000 daltons. Proteolysis, as a source for these diverse components, was ruled out both by studies employing protease inhibitors and experiments employing thrombin which indicated that no helical denaturation had occurred during extraction. A comparison with standard collagen preparations suggested that the major bands present in these samples corresponded to the alpha 1-, alpha 2-, and alpha 3-chains of type V collagen. The data also showed that the major helical organization of these chains was [alpha 1(V)]2 alpha 2(V). Data suggesting that proteolysis can occur during the chromatographic separation of the individual alpha-chains are presented. This proteolysis was sensitive to inhibitors and its possible role in modifying the chain composition of type from calvaria and other tissues is discussed. Unique cyanogen bromide peptides distinguishable from those of type I and type V were present in these precipitates and suggests the presence of novel collagen types. The small amounts of these collagens precluded a determination of the exact nature of these components.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D001842:Bone and Bones / Q000032:analysis*; D003094:Collagen / Q000032:analysis* / Q000378:metabolism; D006801:Humans; D008970:Molecular Weight; D012886:Skull / Q000032:analysis / Q000196:embryology
chemical_list: D000596:Amino Acids; D003094:Collagen