Structure of Chlamydomonas reinhardtii THB1, a group 1 truncated hemoglobin with a rare histidine-lysine heme ligation

THB1 is one of several group 1 truncated hemoglobins (TrHb1s) encoded in the genome of the unicellular green alga Chlamydomonas reinhardtii. THB1 expression is under the control of NIT2, the master regulator of nitrate assimilation, which also controls the expression of the only nitrate reductase in...

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Published in:Acta crystallographica. Section F, Structural biology and crystallization communications Structural biology and crystallization communications, 2015-06, Vol.71 (6), p.718-725
Main Authors: Rice, Selena L., Boucher, Lauren E., Schlessman, Jamie L., Preimesberger, Matthew R., Bosch, Jürgen, Lecomte, Juliette T. J.
Format: Article
Language:English
Subjects:
2/2 hemoglobin
Algal Proteins - chemistry
Algal Proteins - genetics
Amino Acid Motifs
Chlamydomonas reinhardtii - chemistry
Chlamydomonas reinhardtii - metabolism
Crystallography, X-Ray
distal ligand
Escherichia coli - genetics
Escherichia coli - metabolism
Gene Expression
Genes
Heme - chemistry
Hemoglobin
Histidine - chemistry
Iron - chemistry
Ligands
Lysine - chemistry
lysine coordination
Models, Molecular
Molecular Sequence Data
Nitrate Reductase - chemistry
Nitrate Reductase - genetics
Nitrates
nitric oxide dioxygenase
nitrogen metabolism
Protein Binding
Protein Folding
Protein Structure, Secondary
Protein Structure, Tertiary
Recombinant Proteins - chemistry
Recombinant Proteins - genetics
Research Communications
Structural Homology, Protein
Truncated Hemoglobins - chemistry
Truncated Hemoglobins - genetics
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Summary:THB1 is one of several group 1 truncated hemoglobins (TrHb1s) encoded in the genome of the unicellular green alga Chlamydomonas reinhardtii. THB1 expression is under the control of NIT2, the master regulator of nitrate assimilation, which also controls the expression of the only nitrate reductase in the cell, NIT1. In vitro and physiological evidence suggests that THB1 converts the nitric oxide generated by NIT1 into nitrate. To aid in the elucidation of the function and mechanism of THB1, the structure of the protein was solved in the ferric state. THB1 resembles other TrHb1s, but also exhibits distinct features associated with the coordination of the heme iron by a histidine (proximal) and a lysine (distal). The new structure illustrates the versatility of the TrHb1 fold, suggests factors that stabilize the axial ligation of a lysine, and highlights the difficulty of predicting the identity of the distal ligand, if any, in this group of proteins.
ISSN:2053-230X
1744-3091
2053-230X
1744-3091
DOI:10.1107/S2053230X15006949