title: Crystal structures of two hemoglobin components from the midge larva Propsilocerus akamusi (Orthocladiinae, Diptera).
abstract: The polymorphic components of hemoglobin (Hb) of the midge larva Propsilocerus akamusi were classified into two distinct types dependent on their spectroscopic properties, normal absorption (N) and low absorption (L). Analyses of the amino acid sequences of component VII (N-type Hb) and component V (L-type Hb) from P. akamusi indicated that one remarkable difference is the replacement of the distal histidine (His) with isoleucine (Ile) in component V. To clarify the structural differences between the two Hb components, we determined the crystal structures of components V and VII at resolutions of 1.64 A and 1.50 A, respectively. These crystal structures indicated a short additional helix comprising three amino acid residues at the C-terminal region in component V, and a typical globin fold including eight helices in component VII. Comparison of the heme regions of the Hb components suggests that the structural changes of the heme region in component V on ligation differ from that of usual Hb.
authors.affiliation: Advanced Research Institute for the Sciences and Humanities, Nihon University, Chiyoda-ku, Tokyo 102-8251, Japan.
authors.forename: Takao
authors.initials: T
authors.lastname: Kuwada
authors.forename: Tomokazu
authors.initials: T
authors.lastname: Hasegawa
authors.forename: Shu
authors.initials: S
authors.lastname: Sato
authors.forename: Isamu
authors.initials: I
authors.lastname: Sato
authors.forename: Koichi
authors.initials: K
authors.lastname: Ishikawa
authors.forename: Takashi
authors.initials: T
authors.lastname: Takagi
authors.forename: Fumio
authors.initials: F
authors.lastname: Shishikura
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D003460:Crystallization; D004175:Diptera / Q000737:chemistry* / Q000235:genetics; D006418:Heme / Q000378:metabolism; D006454:Hemoglobins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D019476:Insect Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D007814:Larva; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D014961:X-Ray Diffraction
chemical_list: D006454:Hemoglobins; D019476:Insect Proteins; D006418:Heme