Decorin is a small leucine-rich chondroitin/dermatan sulfate proteoglycan reported to interact with fibrillar collagens through its protein core and to localize at d and e bands of the collagen fibril banding pattern. Using a solid-phase assay, we have determined the interaction of peptides derived by CNBr cleavage of type I and type II collagen with decorin extracted from bovine tendon and its protein core and with a recombinant decorin preparation. At least five peptides have been found to interact with all three decorin samples. The interaction of peptides with tendon decorin has a dissociation constant in the nanomolar range. The triple helical conformation of the peptide trimeric species is a necessary requisite for the binding. All positive peptides have a region within the d and e bands of collagen fibrils. Two chemical derivatives of collagens and of positive peptides were prepared by N-acetylation and N-methylation of the primary amino group of Lys/Hyl side chains. Chemical modifications performed in mild conditions do not significantly alter the thermal stability of peptide trimeric species whereas they affect the interaction with decorin: N-acetylation eliminates both the positive charge and the binding to decorin, whereas N-methylation preserves the cationic character and modulates the binding. We conclude that decorin makes contacts with multiple sites in type I collagen and probably also in type II collagen and that some collagen Lys/Hyl residues are essential for the binding.Keywords: collagen; decorin; collagen peptides; proteoglycans; protein-protein interactions.Decorin is a member of the family of extracellular matrix (ECM) proteoglycans characterized by a protein core containing 10 tandem leucine-rich repeats, each of about 24 amino acids, flanked by cysteine clusters. The N-terminal domain carries one chondroitin/dermatan sulfate glycosaminoglycan chain and the protein core also has three consensus sites for N-linked oligosaccharides [1,2]. Leucinerich repeats are involved in protein-protein interactions and have been found in a large number of proteins as well as small leucine-rich proteoglycans (PGs), such as biglycan, fibromodulin and lumican [1,3,4].Decorin is considered a key regulator of the assembly and function of many ECMs. Decorin interacts with a variety of ECM proteins, e.g. with several collagen types, fibronectin and thrombospondin. Collagens have a characteristic triple helical conformation, due to the repetition of triplets Gly-X-Y. The triple helix has a high surface to volume ratio and the side chains of all X and Y residues are accessible by the solvent, X more than Y positions [5]. These geometric and molecular aspects determine the ability of many collagen types to self-associate, leading to defined supramolecular structures, and collagen propensity to interact with many ligands [6].The specific association of decorin with collagens has been reviewed [1,2]. In particular, decorin plays a role in lateral growth of collagen fibrils, delaying the lateral assembly on the sur...

The mitochondrial genome size of 26 different Schizosaccharomyces pombe strains varies between 17.6 and 24.6 kilobase pairs due to the presence or absence of introns. One of these is the group II intron in the gene encoding apocytochrome b (cob: intron cobI1). Partial DNA sequences of continuous cob genes from six strains (including strain EF1: Trinkl et al. 1985) revealed identical nucleotide sequence in the region where the group II intron is inserted in the mosaic form of the gene. In contrast, analysis of the mosaic cob gene in strain UCD-FstI revealed several base pair changes in the exon regions flanking the splice point, compared with the continuous genes and with the mosaic cob gene in strain 50 (Lang et al. 1985). The base pair differences between the exons of the two mosaic cob genes and the identity of exons in all continuous cob genes argue in favour of the two cob introns in strains 50 and UCD-FstI as independent later acquisitions of the genes, rather than loss of the intron from a common mosaic ancestor of all strains. Other introns present in some but not all strain include two group I introns without open reading frame in the gene encoding subunit 1 of cytochrome c oxidase (cox1: introns cox1I2a and cox1I3), and two group I introns with open reading frames in the same gene (introns cox1I1 and cox1I2b).

In this paper we report the inability of four group I introns in the gene encoding subunit I of cytochrome c oxidase (cox1) and the group II intron in the apocytochrome b gene (cob) to splice autocatalytically. Furthermore we present the characterization of the first cox1 intron in the mutator strain anar-14 and the construction and characterization of strains with intronless mitochondrial genomes. We provide evidence that removal of introns at the DNA level (termed DNA splicing) is dependent on an active RNA maturase. Finally we demonstrate that the absence of introns does not abolish homologous mitochondrial recombination.

No abstract

Nucleic Acids Research Strain-dependent variation of intron-exon pairings in a group II intron of Schizosaccharomyces pombe