Beat Trueb

Type VI collagen is a major component of the human cornea

Collagen type VI is shown to be present in the human cornea. This finding is based on comparative peptide mapping relative to type VI collagen isolated from placenta and on immunoblotting using antibodies specific for human type VI collagen. Scanning of polyacrylamide gels indicates that type VI collagen comprises as much as one quarter of the dry weight of the cornea. Indirect immunofluorescence shows this collagen to be distributed throughout the corneal stroma. Thus, type VI collagen must be considered a major component of the extracellular matrix of the human cornea.

Characterization of FGFRL1, a novel fibroblast growth factor (FGF) receptor preferentially expressed in skeletal tissues.

Clones for a novel transmembrane receptor termed FGFRL1 were isolated from a subtracted, cartilage-specific cDNA library prepared from chicken sterna. Homologous sequences were identified in other vertebrates, including man, mouse, rat and fish, but not in invertebrates such as Caenorhabditis elegans and Drosophila. FGFRL1 was expressed preferentially in skeletal tissues as demonstrated by Northern blotting and in situ hybridization. Small amounts of the FGFRL1 mRNA were also detected in other tissues such as skeletal muscle and heart. The novel protein contained three extracellular Ig-like domains that were related to the members of the fibroblast growth factor (FGF) receptor family. However, it lacked the intracellular protein tyrosine kinase domain required for signal transduction by transphosphorylation. When expressed in cultured cells as a fusion protein with green fluorescent protein, FGFRL1 was specifically localized to the plasma membrane where it might interact with FGF ligands. Recombinant FGFRL1 protein was produced in a baculovirus system with intact disulfide bonds. Similar to FGF receptors, the expressed protein interacted specifically with heparin and with FGF2. When overexpressed in MG-63 osteosarcoma cells, the novel receptor had a negative effect on cell proliferation. Taken together our data are consistent with the view that FGFRL1 acts as a decoy receptor for FGF ligands.

The two splice variants of collagen XII share a common 5′ end

The short splice variant of collagen XII is composed of 1960 amino acid residues. This polypeptide contains the same signal peptide and the same carboxy-terminus as the long splice variant, but lacks an internal fragment of 1164 amino acid residues. Thus, the two variants of collagen XII are not created by the use of two different transcription initiation sites as generally assumed, but result from the inclusion or skipping of several exons located within the collagen XII gene.

Synthesis and quantitation of glucitollysine, a glycosylated amino acid elevated in proteins from diabetics

Abstract A method for preparative synthesis of glucitollysine in high yield is described. It is shown that this compound is useful as a standard for the determination of nonenzymatic glycosylation of proteins.

Molecular cloning of a novel ras-like protein from chicken

We have isolated a cDNA clone from a chicken DNA expression library which codes for a ras‐like polypeptide of 216 amino acid residues. This polypeptide is closely related to the human protein TC4 and to the yeast protein Spil, two novel proteins that may be involved in the coordination of the cell cycle. In the amino‐terminal region, the three polypeptides possess a P‐loop motif characteristic of GTP‐binding proteins. At the carboxy‐terminal end, however, they lack the typical CAAX‐box which is usually responsible for membrane anchorage of ras‐like proteins. It is therefore likely that the three polypeptides define a new subclass of GTP‐binding proteins within the ras‐like superfamily.

The tissue form of chicken type VI collagen

We have purified intact type VI collagen from chicken gizzard. The protein was found to consist of a 130 kDa, a 140 kDa and a 180–200 kDa subunit. The 130 kDa and 140 kDa subunits were obtained in equimolar amounts and identified as the α2 (VI) and the α1 (VI) chains, respectively. The third subunit was usually obtained in the form of 3–4 closely related polypeptides, which may represent different processing or modification products of the α3 (VI) chain.