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Humboldt-Universität zu Berlin - Experimentelle Biophysik

Dr. Matthias Broser

 

Room:  404

Email:  matthias.broser@hu-berlin.de

Tel:     (030) 2093 8646

Rhodopsins are light responsive proteins, harboring a retinal cofactor as chromophore. They are found in all three domains of life. While the “classical” animal Rhodopsin in the photoreceptor cell of the eye represents prototypical G-protein coupled receptors, microbial rhodopsins prevalently present in Achaea, Bacteria, and lower Eukaryotes show a wide variation of functionalities [1]. In the early 1970s , the first described member of this protein family is the light-driven proton-pump Bacteriorhodopsin from Halobacterium salinarum  [2]. Since then – particularly stimulated by the availability of genomic information - many other, distinct microbial type rhodopsins have been found, acting as ion pumps, light-gated ion channels, and light sensors [1]. Common for these proteins is the photo-induced all-trans to 13-cis isomerisation of the retinal cofactor. Over the past decade many insights into how this initial photochemical reaction can enable such a broad variability of biochemical features, arose from the elucidation of the three-dimensional structures of unique proteins by protein crystallography [1].

The aim of my project is to expand our knowledge about the mode of action of microbial rhodopsins to the recently identified unusual histidine kinase rhodopsins [3]. Therefore representative members of these modular proteins, in which the rhodopsin domain is directly coupled to a histidine kinase, are expressed heterologously in various expression systems to obtain a protein preparation suitable for x-ray crystallographic approaches.

 

 

[1] Ernst O., Lodowski D.T., Elstner M., Hegemann P., Brown L.S., Kandori H. (2014) "Microbial and Animal Rhodopsins: Structures, Functions, and Molecular Mechanisms" Chem. Rev., 114 (1): 126–163.

 

[2] Oesterhelt D.,Stoeckenius W. (1971) "Rhodopsin-like Protein from the Purple Membrane of Halobacterium halobium " Nature New Biology, 233: 149-152.

 

[3] Luck M, Mathes T., Bruun S., Fudim R., Hagedorn R., Nguyen T.,KateriyaS., Kennis J.T.M., Hildebrandt P.,Hegemann P. (2012) "A Photochromic Histidine Kinase Rhodopsin (HKR1) That Is Bimodally Switched by Ultraviolet and Blue Light" Journal of Biological Chemistry, 287(47): 40083–40090.