ABSTRACT
We have previously identified three distinctive amino acid sequences from type IV collagen which specifically bound to heparin and also inhibited the binding of heparin to intact type IV collagen. One of these chemically synthesized domains, peptide Hep-I, has the sequence TAGSCLRKFSTM and originates from the a1(noncollagenous [NC1]) chain of type IV collagen (Koliakos, G. G., K. K. Koliakos, L. T. Furcht, L. A. Reger, and E. C. Tsilibary. 1989. J. Biol. Chem. 264:2313-2323). We describe in this report that this same peptide also bound to intact type IV collagen in solid-phase assays, in a dose-dependent and specific manner. Interactions between peptide Hep-I and type IV collagen in solution resulted in inhibition of the assembly process of this basement membrane glycoprotein. Therefore, peptide Hep-I should represent a major recognition site in type IV collagen when this protein polymerizes to form a network. In addition, solid phase-immobilized peptide Hep-I was able to promote the adhesion and spreading of bovine aortic endothelial cells. When present in solution, peptide Hep-I competed for the binding of these cells to type IV collagen- and NC1 domain-coated substrata in a dose-dependent manner. Furthermore, radiolabeled peptide Hep-I in solution also bound to endothelial cells in a dose-dependent and specific manner. The binding of radiolabeled Hep-I to endothelial cells could be inhibited by an excess of unlabeled peptide. Finally, in the presence of heparin or chondroitin/dermatan sulfate glycosaminoglycan side chains, the binding of endothelial cells to peptide Hep-I and NC1 domain-coated substrates was also inhibited. We conclude that peptide Hep-I should have a number of functions. The role of this type IV collagen-derived sequence in such diverse phenomena as self-association, heparin binding and cell binding and adhesion makes Hep-I a crucial domain involved in the determination of basement membrane ultrastructure and cellular interactions with type IV collagen-containing matrices.
Subject(s)
Collagen/chemistry , Amino Acid Sequence , Animals , Aorta , Cattle , Cell Adhesion/physiology , Cell Movement/physiology , Endothelium, Vascular/cytology , Endothelium, Vascular/metabolism , Heparin/metabolism , In Vitro Techniques , Kinetics , Molecular Sequence Data , Peptide Fragments/metabolism , Protein Binding , Structure-Activity RelationshipABSTRACT
Using less stringent hybridization conditions and cloned viral DNA probes representing the avian sarcoma virus gag, pol, env, and long terminal repeat (LTR) gene sequences, we detected related sequences in two avian species purportedly lacking all endogenous avian leukosis viruses, the ev- chicken and the Japanese quail. The blot hybridization patterns obtained with the various probes suggest the presence of between 40 and 100 copies of retrovirus-related sequences in the genomes of these two species. An ev- chicken genomic DNA library was prepared and screened with gag-specific and pol-specific DNA probes. Several different clones were obtained from this library and characterized. Analysis of these clones revealed that the retrovirus-related gene sequences are linked in the order LTR-gag-pol-env-LTR, a structure indicative of a complete provirus. These data indicate the presence of previously unidentified endogenous retrovirus species in avian cells, suggesting that under the appropriate conditions of hybridization additional, more distantly evolved families of endogenous retrovirus genes may be identified in vertebrate species.
