Overview of Porphyrin Distortions and Their Impact on Protein Function

Tetrapyrroles serve as a class of small molecules that can perform diverse and complex reactions. From the transport and storage of oxygen in animals to the conversion of light into chemical energy in plants, these macrocyclic cofactors are essential to life on earth.¹ The most well-studied of the tetrapyrrole family are the iron containing heme porphyrins. In the absence of a protein environment, heme porphyrins take a planar conformation, however, when in complex with protein, their conformation is often nonplanar due to forces exerted by the protein.² Early research in this field utilized X-ray crystallography, spectroscopy, theoretical calculations, and molecular modeling to begin the characterization of porphyrin distortions. In 1997, Jentzen et al. developed the normal-coordinate structural decomposition method, allowing for the classification and quantification of out-of-plane and in-plane distortions of porphyrin compounds.³ Continued research and a growing database of nonplanar porphyrins demonstrated conserved out-of-plane distortions within different classes of enzymes, suggesting a direct correlation between the type of distortion and protein function^4,5. One of the more outstanding questions still surrounding this topic is to what extent these deformations impact the biochemical functions and electronic properties of various proteins. With the knowledge of how distorted porphyrin cofactors influence protein function, as well as how to induce distortions of tetrapyrroles, we can ultimately gain more control over essential proteins.

 

References:

1. J.A. Shelnutt, X. Song, J. Ma, S. Jia, W. Jentzen, C.J. Medforth. Chem. Soc. Rev. 1998. 27 (31-41).

2. K.K. Anderson, J.D. Hobbs, L. Luo, K.D. Stanley, J.M.E. Quirke, J.A. Shelnutt. J. Am. Chem. Soc. 1993. 115 (12346-12352).

3. W. Jentzen, X. Song, J.A. Shelnutt. J. Phys. Chem. 1997. 101 (1684-1699).

4. W. Jentzen, M.C. Simpson, J.D. Hobbs, X. Song, T. Ema, N.Y. Nelson, C.J. Medforth, K.M. Smith, M. Veyrat, M. Mazzanti, R. Ramasseul, J.-C. Marchon, T. Takeuchi, W.A. Goddard, J.A. Shelnutt. J. Am. Chem. Soc. 1995. 117 (11085-11097).

5. W. Jentzen, J. Ma, J.A. Shelnutt. Biophysical Journal. 1998. 74 (753-763).