Thermophiles membrane-bound enzymes

A section on protein structural chemistry in archaea includes Chapters 5 through 7, respectively, by D. Oesterhelt on the structure and function of photoreceptor proteins in the Halobacteriaceae J. Lanyi on the structure and function of ion-transport rhodopsins in extreme halophiles and R. Hensel on proteins of extreme thermophiles. In a section on cell envelopes (Chapters 8-10), O. Kandler and H. Konig discuss the structure and chemistry of archaeal cell walls M. Kates reviews the chemistry and function of membrane lipids of archaea and L.I. Hochstein covers membrane-bound proteins (enzymes) in archaea. 

In 1997, Georg E. Schulz in Freiburg succeeded in determining the structure of the membrane-bound squalene-hopene cyclase from the thermophilic microorganism Alicyclobacillus acidocaldar ms (Fig. 3.53 and Fig. 3.54). [258] The enzyme consists of two domains of approximately equal size. Between the two is a cavity with a volume of 1200 A, which contains the active site this is accessible through a non-polar channel in domain 2 (Fig. 3.55). 

The Mg2+-activated ATPase (or ATP synthase) is made up of two parts. The Fj component is the catalytic, Mg2+-binding, extrinsic membrane protein composed of five different subunits, a, (3, y, S and e. The F0 component is an intrinsic membrane complex that contains three subunits, a, b and c, and mediates proton translocation. The F, protein is bound to the membrane through interaction with F0. The complexity of the F,F0 enzyme has presented many difficulties. Hie greatest advances have been made for the bacterial enzymes, notably for thermophiles, Escherichia coli and Rhodospirillum rubrum, where progress has been made in the purification of subunits and their reconstitution into membranes, and the identification of binding sites for Mg2+ and nucleotides on the Fi subunits.300 FiF0 preparations can be incorporated into liposomes and display H+ translocation, ATP-P, exchange and ATP synthesis.301... 

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