Title:Mini Heme-Proteins: Designability of Structure and Diversity of Functions
Volume: 18
Issue: 11
Author(s): Jagdish Rai*
Affiliation:
- Institute of Forensic Science and Criminology, Panjab University, Chandigarh, Pin code 160014,India
Keywords:
Heme protein, Designed protein, Heme-peptide complex, designed heme-protein, mini-protein, soret band, hemeligation.
Abstract: Natural heme proteins may have heme bound to poly-peptide chain as a cofactor via noncovalent
forces or heme as a prosthetic group may be covalently bound to the proteins. Nature has used
porphyrins in diverse functions like electron transfer, oxidation, reduction, ligand binding, photosynthesis,
signaling, etc. by modulating its properties through diverse protein matrices. Synthetic chemists
have tried to utilize these molecules in equally diverse industrial and medical applications due to their
versatile electro-chemical and optical properties. The heme iron has catalytic activity which can be
modulated and enhanced for specific applications by protein matrix around it. Heme proteins can be designed
into novel enzymes for sterio specific catalysis ranging from oxidation to reduction. These designed
heme-proteins can have applications in industrial catalysis and biosensing. A peptide folds
around heme easily due to hydrophobic effect of the large aromatic ring of heme. The directional property
of co-ordinate bonding between peptide and metal ion in heme further specifies the structure. Therefore
heme proteins can be easily designed for targeted structure and catalytic activity. The central aromatic
chemical entity in heme viz. porphyrin is a very ancient molecule. Its presence in the prebiotic
soup and in all forms of life suggests that it has played a vital role in the origin and progressive evolution
of living organisms. Porphyrin macrocycles are highly conjugated systems composed of four modified
pyrrole subunits interconnected at their α -carbon atoms via methine (=CH−) bridges. Initial minimalist
models of hemoproteins focused on effect of heme-ligand co-ordinate bonding on chemical reactivity,
spectroscopy, electrochemistry and magnetic properties of heme. The great sensitivity of these
spectroscopic features of heme to its surrounding makes them extremely useful in structural elucidation
of designed heme-peptide complexes. Therefore heme proteins are easier to work on for designing novel
proteins for industrial and medical applications.
