The crystal structure of a tetrameric hemoglobin in a partial hemichrome state

AUTOR(ES)

Riccio, Antonio

FONTE

The National Academy of Sciences

RESUMO

Tetrameric hemoglobins are the most widely used systems in studying protein cooperativity. Allosteric effects in hemoglobins arise from the switch between a relaxed (R) state and a tense (T) state occurring upon oxygen release. Here we report the 2.0-Å crystal structure of the main hemoglobin component of the Antarctic fish Trematomus newnesi, in a partial hemichrome form. The two α-subunit iron atoms are bound to a CO molecule, whereas in the β subunits the distal histidine residue is the sixth ligand of the heme iron. This structure, a tetrameric hemoglobin in the hemichrome state, demonstrates that the iron coordination by the distal histidine, usually associated with denaturing states, may be tolerated in a native-like hemoglobin structure. In addition, several features of the tertiary and quaternary organization of this structure are intermediate between the R and T states and agree well with the R → T transition state properties obtained by spectroscopic and kinetic techniques. The analysis of this structure provides a detailed pathway of heme–heme communication and it indicates that the plasticity of the β heme pocket plays a role in the R → T transition of tetrameric hemoglobins.

Documentos Relacionados

• Correlation between Hemichrome Stability and the Root Effect in Tetrameric Hemoglobins
• Expression of fully functional tetrameric human hemoglobin in Escherichia coli.
• Crystal structure of the tetrameric Mad1–Mad2 core complex: implications of a ‘safety belt’ binding mechanism for the spindle checkpoint
• Sulfide binding is mediated by zinc ions discovered in the crystal structure of a hydrothermal vent tubeworm hemoglobin
• Preparation, properties, and plasma retention of human hemoglobin derivatives: comparison of uncrosslinked carboxymethylated hemoglobin with crosslinked tetrameric hemoglobin.