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Anabaena sensory rhodopsin transducer The family of bacterial Anabaena sensory rhodopsin transducers are likely to bind sugars or related metabolites. The entire protein is comprised of a single globular domain with an eight-stranded beta-sandwich fold. There are a few characteriztics which define this beta-sandwich fold as being distinct from other so-named folds, and these are: 1) a well conserved tryptophan, usually following a polar residue, present at the start of the first strand; this tryptophan appears to be central to a hydrophobic interaction required to hold the two beta-sheets of the sandwich together, and 2) a nearly absolutely conserved asparagine located at the end of the second beta-strand, that hydrogen bonds with the backbone carbonyls of the residues 2 and 4 positions downstream from it, thereby stabilising the characteriztic tight turn between strands 2 and 3 of the structure.
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