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A model of Heme B cofactor.

A hemeprotein (or haemprotein; also hemoprotein or haemoprotein), or heme protein, is a metalloprotein containing a heme prosthetic group- an organic compound that allows a protein to carry out several functions that it cannot do alone.[1] Heme remains bound to the protein permanently, either covalently or noncovalently bound or both.[2]


Hemeproteins probably evolved to incorporate the iron (Fe) atom contained within the protoporphyrin IX ring of heme into proteins. As it makes hemeproteins responsive to molecules that can bind divalent iron (Fe), this strategy has been maintained throughout evolution as it plays crucial physiological functions. Oxygen (O2) nitric oxide (NO), carbon monoxide (CO) and hydrogen sulfide (H2S) bind to the iron atom in heme proteins. Once bound to the prosthetic heme groups, these molecules can modulate the activity/function of those hemeproteins, affording signal transduction. Therefore, when produced in biologic systems (cells), these gaseous molecules are referred to as gasotransmitters.




Hemoglobin and Myoglobin[edit]


His-F8 of the myoglobin, also known as the proximal histidine is covalently bonded to the 5th coordination position of the iron. Oxygen interacts with the distal His by ways of a hydrogen bond,not a covalent one. It binds to the 6th coordination position of the iron, His-E7 of the myoglobin binds to the Oxygen that is now covalently bonded to the iron. The same occurs for the hemoglobin, however, being a protein with 4 subunits, the hemoglobin contains 4 heme, therefore, allowing 4 Oxygen atoms to bind to the heme.



Myoglobin and hemoglobin are of obvious critical importance to vertebrate life, yet they are also studied because they serve as excellent, well-characterized models for illustrating the principles of protein structure, dynamics, and function. Keep in mind that the concepts you will be learning in this exercise, especially regarding oxygen binding and allostery, are also directly applicable to the study of enzyme kinetics, more specifically substrate binding and allosteric regulation of enzyme activity.






Cytochrome c Oxidase[edit]


External links[edit]


  1. ^ prosthetic group: Definition from Answers.com
  2. ^ a b Knovel - Knovel Content
  3. ^ Gibney, Brian R.; Elvekrog, M. M.; Reedy, C. J. (18 September 2007). "Development of a heme protein structure electrochemical function database". Nucleic Acids Research 36 (Database): D307–D313. doi:10.1093/nar/gkm814. 
  4. ^ Heme Protein Database