De Novo Design and Molecular Assembly of a Transmembrane Diporphyrin-Binding Protein Complex

Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
Journal of the American Chemical Society (Impact Factor: 11.44). 10/2010; 132(44):15516-8. DOI: 10.1021/ja107487b
Source: PubMed

ABSTRACT The de novo design of membrane proteins remains difficult despite recent advances in understanding the factors that drive membrane protein folding and association. We have designed a membrane protein PRIME (PoRphyrins In MEmbrane) that positions two non-natural iron diphenylporphyrins (Fe(III)DPP's) sufficiently close to provide a multicentered pathway for transmembrane electron transfer. Computational methods previously used for the design of multiporphyrin water-soluble helical proteins were extended to this membrane target. Four helices were arranged in a D(2)-symmetrical bundle to bind two Fe(II/III) diphenylporphyrins in a bis-His geometry further stabilized by second-shell hydrogen bonds. UV-vis absorbance, CD spectroscopy, analytical ultracentrifugation, redox potentiometry, and EPR demonstrate that PRIME binds the cofactor with high affinity and specificity in the expected geometry.

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