The solution structure of the recombinant hemoglobin from the cyanobacterium Synechocystis sp. PCC 6803 in its hemichrome state.
The product of the cyanobacterium Synechocystis sp. PCC 6803 gene slr2097 is a 123 amino acid polypeptide chain belonging to the truncated hemoglobin family. Recombinant, ferric heme-reconstituted Synechocystis sp. PCC 6803 hemoglobin displays bis-histidine coordination of the iron ion. In addition, this protein is capable of covalently attaching a reactive histidine to the heme 2-vinyl group. The structure of the protein in the low-spin ferric state with intact vinyl substituents was solved by NMR methods. It was found that the structure differs from that of known truncated hemoglobins primarily in the orientation of the E helix, which carries His46 (E10) as the distal ligand to the iron; the length and orientation of the F helix, which carries His70 (F8) as the proximal ligand to the iron; and the H-helix, which carries His117 (H16), the reactive histidine. Regions of enhanced flexibility include the short A helix, the loop connecting the E and F helices, and the last seven residues at the carboxy end. The structural data allowed for the rationalization of physical properties of the cyanobacterial protein, such as fast on-rate for small ligand binding, unstable apoprotein fold, and cross-linking ability. Comparison to the truncated hemoglobin from the green alga Chlamydomonas eugametos also suggested how the endogenous hexacoordination affected the structure.
Falzone
Christopher J
CJ
Department of Chemistry and the Center for Biomolecular Structure and Function, The Pennsylvania State University, University Park, PA 16802, USA. cxf14@psu.edu
Christie Vu
B
B
Scott
Nancy L
NL
Lecomte
Juliette T J
JT
D000595:Amino Acid Sequence; D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D001665:Binding Sites; D002696:Chlamydomonas / Q000737:chemistry; D000458:Cyanobacteria / Q000737:chemistry*; D006418:Heme / Q000737:chemistry / Q000378:metabolism; D006454:Hemoglobins / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D011166:Porphyrins / Q000737:chemistry; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012996:Solutions; D055672:Static Electricity; D054793:Truncated Hemoglobins
D001426:Bacterial Proteins; D006454:Hemoglobins; D011166:Porphyrins; D011994:Recombinant Proteins; D012996:Solutions; D054793:Truncated Hemoglobins; D006418:Heme