Catalytic enzymes swapping

In be complexes bci complexes of mitochondria and bacteria and b f complexes of chloroplasts), the catalytic domain of the Rieske protein corresponding to the isolated water-soluble fragments that have been crystallized is anchored to the rest of the complex (in particular, cytochrome b) by a long (37 residues in bovine heart bci complex) transmembrane helix acting as a membrane anchor (41, 42). The great length of the transmembrane helix is due to the fact that the helix stretches across the bci complex dimer and that the catalytic domain of the Rieske protein is swapped between the monomers, that is, the transmembrane helix interacts with one monomer and the catalytic domain with the other monomer. The connection between the membrane anchor and the catalytic domain is formed by a 12-residue flexible linker that allows for movement of the catalytic domain during the turnover of the enzyme (Fig. 8a see Section VII). Three different positional states of the catalytic domain of the Rieske protein have been observed in different crystal forms (Fig. 8b) (41, 42) ... 

In a different approach, hybrids of P540 BM3 and neuronal nitric oxide synthase (nNOS) were generated in which the heme and reductase domains of the respective enzymes were swapped, while maintaining the natural domain order [112, 209]. Such hybrids could successfully be expressed in E. coli and were shown to be catalytically active [162, 209], With snch hybrids,... 

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