Download MendeleyThe crystal structure of a tetrameric hemoglobin in a partial hemichrome state
Riccio, A., Vitagliano, L., di Prisco, G., Zagari, A., Mazzarella, L.(2002) Proc Natl Acad Sci U S A 99: 9801-9806
- PubMed: 12093902
- DOI: https://doi.org/10.1073/pnas.132182099
- Primary Citation of Related Structures:
1LA6 - PubMed Abstract:
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-A crystal structure of the main hemoglobin component of the Antarctic fish Trematomus newnesi, in a partial hemichrome form. The two alpha-subunit iron atoms are bound to a CO molecule, whereas in the beta 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 beta heme pocket plays a role in the R --> T transition of tetrameric hemoglobins.
Organizational Affiliation:
Istituto di Biochimica delle Proteine ed Enzimologia, Consiglio Nazionale delle Ricerche, I-80125 Naples, Italy.
