title: The molecular weight and subunit organization of Helisoma trivolvis (Say) hemoglobin: light-scattering and scanning transmission electron microscopic studies.
abstract: The hemoglobin of the freshwater snail, Helisoma trivolvis has a molecular weight of 1.77(+/- 0.04) x 10(6) Da as determined by light-scattering measurements at 630 nm. Scanning transmission electron microscopic measurements gave nearly the same particle mass of 1.85(+/- 0.24) x 10(6) Da. The molecular weight of the denatured hemoglobin in 6.0 M GdmCl is found to be 3.96 x 10(5) Da, which is close to one-fifth of the mass of the parent hemoglobin. The molecular weight data based on light-scattering and STEM microscopy is consistent with a 10-subunit structure comprising five disulfide-linked dimers, as opposed to a 12-subunit assembly proposed by Ilan et al. (1986), which would necessitate a higher particle mass. Analysis of the molecular weight and the sedimentation data of H. trivolvis hemoglobin, suggests a compact two-layer ring structure of decamers of about 200 A to 250 A diameter, stabilized by disulfide-linkages between the subunits of the two pentameric layers.
authors.affiliation: Department of Chemistry, Fordham University, Bronx, New York, NY 10458, USA.
authors.forename: T T
authors.initials: TT
authors.lastname: Herskovits
authors.forename: M G
authors.initials: MG
authors.lastname: Hamilton
mesh_terms: D000818:Animals; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D004220:Disulfides / Q000737:chemistry; D019791:Guanidine; D006146:Guanidines; D006454:Hemoglobins / Q000737:chemistry*; D008027:Light; D046911:Macromolecular Substances; D017348:Microscopy, Electron, Scanning Transmission; D008970:Molecular Weight; D011489:Protein Denaturation; D012542:Scattering, Radiation; D012908:Snails / Q000737:chemistry*; D014508:Urea
chemical_list: D004220:Disulfides; D006146:Guanidines; D006454:Hemoglobins; D046911:Macromolecular Substances; D014508:Urea; D019791:Guanidine