Biomedical subjects

M Beardmore-Gray

Publications and source records attributed to M Beardmore-Gray.

5 recordsLinked to original sources

PubMed1987

Extended and globular protein domains in cartilage proteoglycans.

Electron microscopy after rotary shadowing and negative staining of the large chondroitin sulphate proteoglycan from rat chondrosarcoma, bovine nasal cartilage and pig laryngeal cartilage demonstrated a unique multidomain structure for the protein core. A main characteristic is a pair of globular domains (diameter 6-8 nm), one of which forms the N-terminal hyaluronate-binding region. They are connected by a 25 nm-long rod-like domain of limited flexibility. This segment is continued by a 280 nm-long polypeptide strand containing most chondroitin sulphate chains (average length 40 nm) in a brush-like array and is terminated by a small C-terminal globular domain. The core protein showed a variable extent of degradation, including the loss of the C-terminal globular domain and sections of variable length of the chondroitin sulphate-bearing strand. The high abundance (30-50%) of the C-terminal domain in some extracted proteoglycan preparations indicated that this structure is present in the cartilage matrix rather than being a precursor-specific segment. It may contain the hepatolectin-like segment deduced from cDNA sequences corresponding to the 3'-end of protein core mRNA [Doege, Fernandez, Hassell, Sasaki & Yamada (1986) J. Biol. Chem. 261, 8108-8111; Sai, Tanaka, Kosher & Tanzer (1986) Proc. Natl. Acad. Sci. 83, 5081-5085; Oldberg, Antonsson & Heinegård (1987) Biochem. J. 243, 255-259].

Animals↗

PubMed1986

Cartilage proteoglycans.

The structure of the protein core of the high molecular weight aggregating proteoglycan from pig laryngeal cartilage has been investigated. Mild trypsin digestion of proteoglycan aggregates released a large (Mr approximately equal to 150K) protein-rich fragment that contained the hyaluronate-binding region (Mr 66K). Rotary-shadowing electron microscopy of this preparation showed it to contain 'double globe' structures, similar to those seen with intact proteoglycans. Interaction studies and immunochemical evidence showed that one of the globular domains was the binding region. The second globular domain did not interact with hyaluronate or share any major antigenic determinants with the binding region and its function remains unknown. Further evidence from rotary shadowing also suggested that the protein core contained a third globular domain at the C-terminal end. The complete protein core sequence thus contains long folded globular protein regions, in addition to the extended regions bearing glycosaminoglycan chains. Studies of proteoglycan turnover in explants of pig articular cartilage showed that proteoglycan fragments were continuously released into the medium during culture. These included large non-aggregating proteoglycan fragments, free binding region and also link protein. Proteoglycans retained within the cartilage matrix remained intact and able to aggregate. Only in the presence of interleukin 1 was there evidence of more extensive proteolytic digestion. The results suggest normal turnover to be a conservative mechanism involving the selective cleavage of proteoglycan close to the hyaluronate-binding region. This releases the major glycosaminoglycan-bearing domain and enables it to diffuse out of the matrix. The site of the initial cleavage appears to be in the region of the N-terminal globular domains.

Animals↗

PubMed1986

The oxidation of glucose by Acinetobacter calcoaceticus: interaction of the quinoprotein glucose dehydrogenase with the electron transport chain.

The coupling of the quinoprotein glucose dehydrogenase to the electron transport chain has been investigated in Acinetobacter calcoaceticus. No evidence was obtained to support a previous suggestion that the soluble form of the dehydrogenase and the soluble cytochrome b associated with it are involved in the oxidation of glucose. Analysis of cytochrome content, and of reduction of cytochromes in membranes by substrates, and of sensitivity to cyanide indicated that glucose, succinate and NADH are all oxidized by way of the same b-type cytochrome(s) and cytochrome oxidases (cytochrome o and cytochrome d). Mixed inhibition studies [with KCN and hydroxyquinoline N-oxide (HQNO)] showed that the b-type cytochrome(s) formed a binary complex with the o-type oxidase and that there was thus no communication between the electron transport chains at the cytochrome level. Measurements of the reduction of ubiquinone-9 by glucose and NADH, and inhibitor studies using HQNO, indicated that the ubiquinone mediates electron transport from both the glucose and NADH dehydrogenases. In some conditions the quinone pool facilitated communication between the 'glucose oxidase' and 'NADH oxidase' electron transport chains, but in normal conditions these chains were kinetically distinct.

Acinetobacter↗

PubMed1983

The absence of quinoprotein alcohol dehydrogenase in Acinetobacter calcoaceticus.

It is shown that the unusual NAD(P)+-independent quinoprotein alcohol dehydrogenase, said previously to be responsible for oxidation of ethanol during growth of Acinetobacter calcoaceticus LMD 79.39, was in fact isolated from an unidentified organism which contained cytochrome c and which has now been lost. Several genuine strains of A. calcoaceticus do not contain cytochrome c nor do they contain a quinoprotein alcohol dehydrogenase. The enzyme responsible for ethanol oxidation in these bacteria is an inducible NAD+-linked alcohol dehydrogenase.

Acinetobacter↗

PubMed1982

The autoreducible cytochromes c of the methylotrophs Methylophilus methylotrophus and Pseudomonas AM1.

The two types of soluble cytochrome c (cytochrome cH and cytochrome cL) found in methylotrophs are completely distinct proteins; one type is not a dimer or degradation product of the other. Free thiol groups are probably not involved in the unusually rapid autoreduction of the cytochromes at high pH. The axial ligands to the haem iron, histidine and methionine, are the same as in other low-spin cytochromes c. The methionine ligand is displaced at high pH by an alternative strong-field ligand. This displacement does not occur on reduction of cytochrome cL by methanol dehydrogenase, but this does not rule out the possibility that the autoreduction mechanism is involved in the interaction of the dehydrogenase and cytochrome c.

Alcohol Oxidoreductases↗