Biomedical subjects

Y Dou

Publications and source records attributed to Y Dou.

39 records · Page 3Linked to original sources

PubMed1993

Ligand diffusion in the distal heme pocket of myoglobin. A primary determinant of geminate rebinding.

There are at least two picosecond kinetic components in the rebinding of NO to native sperm whale myoglobin. Petrich et al. (Petrich, J. W., Lambry, J.-C., Kuczera, K., Karplus, M., Poyart, C., and Martin, J.-L. (1991) Biochemistry 30, 3975-3987) attribute the slowing of the reaction to a movement of the iron atom out of the plane of the heme following ligand dissociation. In contrast, Gibson et al. (Gibson, Q. H., Regan, R., Elber, R., Olson, J. S., and Carver, T. E. (1992) J. Biol. Chem. 267, 22022-22034) have explained multiphasic geminate reactions by diffusion of NO into the distal heme pocket as determined by its detailed structure. O2 and NO rebinding to iron and cobalt derivatives of native, V68F, and V68I sperm whale myoglobin has been examined. Each iron protein shows a biphasic time course of NO rebinding reactions with widely different rates and amplitudes. Although cobalt does not move out of the plane of the porphyrin on ligand removal, the reactions of the iron and cobalt derivatives of each protein were closely similar. The time course of O2 rebinding to cobalt was also similar to that of NO rebinding to iron. These results are consistent with a primary role for the structure of the distal pocket in determining diffusion of ligands away from the metal atom and as a result the time course of picosecond ligand rebinding.

Animals↗

PubMed1992

Ligand-induced protein tyrosine kinase activity in living cells coexpressing intact EGF receptors and receptors with an extensive cytosolic deletion.

A population of stable NIH 3T3 transfectants with two molecular weight classes of membrane-bound EGF receptors encoded by a human EGF receptor cDNA has been identified and characterized. In addition to intact EGF receptors, these cells also express a molecule with an extensive cytosolic deletion. This deletion includes the ligand-activated intrinsic protein tyrosine kinase catalytic domain. Treatment with EGF caused dimerization of intact and truncated receptors, allowing us to assess protein tyrosine kinase activity in the heterodimer isolated from living cells. In contrast to homodimeric complexes with intact EGF receptor only, heterodimers were deficient in protein tyrosine kinase activity. Moreover, physical association between intact and truncated molecules suppressed receptor auto-phosphorylation by EGF receptor protein tyrosine kinase activated by antibody binding in vitro. Evidence presented here supports the idea that protein tyrosine kinase activation is facilitated by interaction between adjacent receptor molecules with intact catalytic domains. Furthermore, molecules with cytoplasmic deletions that are physically associated with kinase-active EGF receptors appear to behave as dominant negative mutations. The HerC cl cells used in this study were selected with methotrexate to amplify the EGF receptor cDNA, and in that sense may resemble certain tumor-derived cells characterized by overexpressed and rearranged EGF receptor genes.

Animals↗

PubMed1991

[Isolation and characteristics of Borrelia burgdorferi from Ixodes persulcatus].

We reported the detailed characteristics of Lyme disease spirochetes (Borrelia burgdorferi), strain H7, isolated from Ixodes persulcatus in Heilongjiang. Cells of strain H7 were 9.8--26.5 microns long and 0.13--0.35 microns wide. There were 1--11 waves with a wavelength of 1.2--3.0 microns and an amplitude of 0.59--1.13 microns. Direction of spires was left. Seven flagella were inserted subterminally at each end of the cell and ends were pointed. 31 degrees C was the optimum cultural temperature in vitro. The major constitutional and antigenic proteins were 21k, 32k and 34k proteins. H7 could react on the patient sera of Xinjiang and Heilongjiang with IFA and western blot. These findings demonstrated that strain H7 belonged to species Borrelia burgdorferi, but was a new "subtype" which differed from the strains isolated from other areas and vectors.

Animals↗