Spectroscopical and functional characterization of the hemoglobin of Nostoc commune (UTEX 584 (Cyanobacterial).
Structural analysis of a monomeric hemoglobin from the cyanobacterium Nostoc commune strain UTEX 584, cyanoglobin (Potts et al. (1992) Science 256, 1690-1692), is presented. Cyanoglobin binds molecular oxygen reversibly, with high oxygen affinity and non-cooperativity. There was no evidence for decreased stability of the pigment at 37 degrees C. Cyanoglobin-specific antibodies showed no cross-reactivity with two reference hemoglobins, leghemoglobin a and sperm whale myoglobin. The absorption spectral properties of cyanoglobin differ significantly from those of the two reference hemoglobins. The spectrum of oxy-cyanoglobin most closely resembles that of an oxy-hemoglobin from the protozoan Tetrahymena pyriformis, a hemoprotein that shares substantial amino-acid sequence identity with cyanoglobin. Met-cyanoglobin possesses spectral characteristics at pH 7.0-9.0 that resemble those of the alkaline met-hemoglobin (a putative hemichrome) of another protozoan, Paramecium caudatum. The spin-state character of met-cyanoglobin is pH-dependent. Met-cyanoglobin does not coordinate the strong-field ligands, cyanide and azide, at pH 7.0. The capacity of cyanoglobin to coordinate cyanide increased with decreasing pH. Far-UV CD spectra of cyanoglobin are indicative of a protein with a significant amount of alpha-helical structure. Data from Soret-region CD spectra suggest that the orientations of the heme moieties in cyanoglobin and leghemoglobin a are similar to one another.
Department of Biochemistry and Anaerobic Microbiology, Virginia Polytechnic Institute and State University, Blacksburg 24061, USA.
M V
MV
Thorsteinsson
D R
DR
Bevan
R E
RE
Ebel
R E
RE
Weber
M
M
Potts
D015153:Blotting, Western; D002942:Circular Dichroism; D000458:Cyanobacteria / Q000737:chemistry*; D004926:Escherichia coli / Q000235:genetics; D006418:Heme / Q000378:metabolism; D006454:Hemoglobins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007874:Leghemoglobin / Q000737:chemistry / Q000276:immunology; D008706:Methemoglobin / Q000737:chemistry; D009211:Myoglobin / Q000276:immunology; D009586:Nitrogen Fixation; D010100:Oxygen / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D013053:Spectrophotometry
D006454:Hemoglobins; D007874:Leghemoglobin; D009211:Myoglobin; D011994:Recombinant Proteins; C011207:cyanhemoglobin; D006418:Heme; D008706:Methemoglobin; D010100:Oxygen