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Eric Martz
The first new influenza virus to emerge as an imminent pandemic threat in the 21st century is H1N1 swine flu. The drug oseltamivir (Tamiflu®) inhibits flu neuraminidase, a component necessary for virus spread, in susceptible flu strains. The development of oseltamivir was guided, in part, by crystallographically determined structures of flu neuraminidase, which is a homotetramer, shown with oseltamivir bound. Oseltamivir was designed to fit N2/N9 (neuraminidases from other strains of flu). Serendipitously, it also fits N1 by induced fit.

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IB Tomasic, MC Metcalf, AI Guce, NE Clark, SC Garman. J. Biol. Chem. 2010 doi: 10.1074/jbc.M110.118588
The human lysosomal enzymes α-galactosidase and α-N-acetylgalactosaminidase share 46% amino acid sequence identity and have similar folds. Using a rational protein engineering approach, we interconverted the enzymatic specificity of α-GAL and α-NAGAL. The engineered α-GAL retains the antigenicity but has acquired the enzymatic specificity of α-NAGAL. Conversely, the engineered α-NAGAL retains the antigenicity but has acquired the enzymatic specificity of the α-GAL enzyme. Comparison of the crystal structures of the designed enzyme to the wild-type enzymes shows that active sites superimpose well, indicating success of the rational design. The designed enzymes might be useful as non-immunogenic alternatives in enzyme replacement therapy for treatment of lysosomal storage disorders such as Fabry disease.

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by Eric Martz
The Ramachandran Principle says that alpha helices, beta strands, and turns are the most likely conformations for a polypeptide chain to adopt, because most other conformations are impossible due to steric collisions between atoms. Check Show Clashes to see where non-bonded atoms are overlapping, and thus in physically impossible positions.

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