Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “ANNELIDA”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 811 records · Page 45Linked to original sources
PubMed1977

Physicochemical and functional properties of Perinereis cultrifera (Grübe) erythrocruorin.

Perinereis erythrocruorin has the following physicochemical properties: So20,w = 55S, corresponding to a molecular weight around 2.7-10(6); minimum molecular weight (on the basis of the heme content) 23 700 +/- 500; isoelectric point 5.1; alpha-helix content approximately 40%. At alkaline pH values in the oxygenated form the 55-S molecules dissociate into subunits with a weight average sedimentation coefficient of 3S, corresponding to a molecular weight approximately 35 000. Deoxygenation of partially dissociated samples promotes association of the 3-S subunits into a 9S component. The functional properties of Perinereis erythrocruorin are characterized by a low cooperativity in oxygen binding (n 1/2 = 1.5) at neutral pH. Cooperativity increases reversibly towards both the acid and alkaline pH range, irrespective of changes in molecular weight. This finding, taken together with the ultracentrifuge results, suggests that a subunit may represent the functional unit of the protein. The pH dependence of the oxygen affinity can be accounted for in terms of a single oxygen linked group with a pK of 8.

Allosteric Site↗
PubMed1980

Amphitrite ornata erythrocruorin. I. Structural properties and characterization of subunit interactions.

A high molecular weight erythrocruorin (Mr approx. 3 . 10(6)) is found in the vascular system of the marine terebellid worm Amphitrite ornata, while a low molecular weight hemoglobin is contained in the coelomic cells. Polyacrylamide gel electrophoresis indicates that Amphitrite erythrocruorin contains three different types of polypeptide chain, of molecular weight approx. 15,000, whereas the molecular weight per heme group is approx. 20,000. These data suggest that only two of three polypeptide chains may be associated with a heme group. The coelomic hemoglobin, which occurs as a monomer, has an apparent molecular weight of approx. 14,000. The circular dichroism spectra of Amphitrite erythrocruorin and of the coelomic protein reveal marked differences in the heme environment, while the alpha-helical contents are not very different (60% and 70%, respectively). Amphitrite erythrocruorin is unusual in its dissociation behavior. Divalent cations are required for maintaining the quaternary structure. In the pH range 7.75--8.5, when the Ca2+ concentration is reduced below 1 mM, the whole molecule (57 S) dissociates into a number of lower molecular weight species (25, 15, 10 and 3 S) which have been correlated with specific subunit structures by electron microscopy. Whole molecules and 25 S subunits are not in equilibrium with the lower molecular weight species and can be isolated from partially dissociated mixtures. In contrast, the lower molecular weight subunits are themselves in a state of rapid equilibrium which is sensitive to cations, protons and oxygen. Of special interest is the dimerization reaction of the 10 S subunits, which appears to be mediated by Ca2+ and conforms to the predictions of the Cann and Goad theory on ligand mediated equilibria. The dissociation of Amphitrite erythrocruorin is readily reversible when the Ca2+ concentration is increased. The subunits obtained at physiological (7.8) or slightly acid (6.5) pH completely reassemble into whole molecules. Reassembly, however, is only partial when dissociation occurs at high pH. The presence of stable intermediates, such as the 15 S species, may facilitate the reassociation process.

Amino Acids↗
PubMed1980

Solution studies on heme proteins. Circular dichroism and optical rotation of Glycera dibranchiata hemoglobins.

Circular dichroism (CD) and optical rotatory dispersion (ORD) spectra of several liganded derivatives of the monomer and polymer hemoglobin components of the marine annelid, Glycera dibranchiata were measured over the wavelength range 650--195 nm. The differences observed between the monomer and polymer components for the heme dichroic bands in the visible, Soret and ultraviolet wavelength regions seem to result from changes in the heme environment, geometry and coordination state of the central heme iron in these proteins. Within the Soret region, the liganded derivatives of the monomer hemoglobin exhibit predominantly negative circular dichroic bands. The heme band at 260 nm is also absent for the monomer hemoglobin. The ORD and CD spectra in the far-ultraviolet, peptide absorbing region suggest also differences in the alpha-helix content of the monomer and polymer hemoglobins. The values for the single-chain G. dibranchiata hemoglobin are in the expected range (about 70% alpha-helix) as predicted by the X-ray structure of this protein. The lower estimates of the alpha-helix content for the polymer hemoglobin (approx. 50%), may reflect the differences in amino acid composition, primary structure and polypeptide chain foldings. Changes in oxidation state and ligand binding appears to have no pronounced effect on the helicity of either the monomer or polymer hemoglobins. The removal of the heme moiety from the monomer hemoglobin did result in a major decrease in its helix content similar to the loss of heme from myoglobin.

Animals↗
PubMed1980

Subunits of the extracellular hemoglobin of Arenicola marina.

The molecular weight of the extracellular hemoglobin of Arenicola marina determined by equilibrium sedimentation is 3.74 +/- 0.12 . 10(6). Its iron content is 0.244 +/- 0.005 wt.% corresponding to a minimum molcular weight of 22 900 +/- 500. Polyacrylamide gel electrophoresis in sodium dodecyl sulfate showed that the hemoglobin dissociated into three subunits: 14 000 (subunit 1), 31 000 (subunit 2) and 49 000 (subunit 3); in the presence of 2-mercaptoethanol four subunits were observed, 14 000 (subunit I), 16 000 (subunit II), 31 000 (subunit III), and 35 000 (subunit IV). Two-dimensional electrophoresis showed that subunit 1 produced subunit I, and subunits 2 and 3 produced subunits I, II and variable amounts of subunits III and IV. Gel filtration of reduced and alkylated A. marina hemoglobin in 6 M guanidinium hydrochloride suggests that the molecular weight of subunits I and II is 17 500 +/- 1000. A. marina hemoglobin appears to consist of at least 5--7 polypeptide chains. It is proposed that some of the polypeptide chains can associate to form dimers (subunits 2, III, IV) or trimers (subunit 3).

Annelida↗
PubMed1991

Evidence that sensitivity to steroid anesthetics appears late in evolution.

The effects of pregnanolone, a steroid anesthetic, were compared with diethyl ether and short chain alkanols in 21 aquatic species from 7 phyla. Loss of righting reflex and escape response were used as indicators of anesthesia. All organisms were anesthetized by diethyl ether and short chain alkanols, but pregnanolone affected only organisms belonging to the phylum Chordata. It is probable that pregnanolone exerts its effect on the gamma-aminobutyric acid (GABA) receptor. Because many invertebrates do possess GABA receptors, our results suggest that a binding site at which steroid binding causes organismal anesthesia appeared early in chordate evolution on a previously existing GABA receptor. The results also appear to exclude a primary lipid bilayer site for steroid anesthetic action.

Alcohols↗