Dysregulation of the complement system is linked to the pathogenesis of a variety of hematological disorders. Eculizumab, an anti-complement C5 monoclonal antibody, is the current standard of care for paroxysmal nocturnal hemoglobinuria (PNH) and atypical hemolytic uremic syndrome (aHUS). However, because of high levels of C5 in plasma, eculizumab has to be administered biweekly by intravenous infusion. By applying recycling technology through pH-dependent binding to C5, we generated a novel humanized antibody against C5, SKY59, which has long-lasting neutralization of C5. In cynomolgus monkeys, SKY59 suppressed C5 function and complement activity for a significantly longer duration compared to a conventional antibody. Furthermore, epitope mapping by X-ray crystal structure analysis showed that a histidine cluster located on C5 is crucial for the pH-dependent interaction with SKY59. This indicates that the recycling effect of SKY59 is driven by a novel mechanism of interaction with its antigen and is distinct from other known pH-dependent antibodies. Finally, SKY59 showed neutralizing effect on C5 variant p.Arg885His, while eculizumab does not inhibit complement activity in patients carrying this mutation. Collectively, these results suggest that SKY59 is a promising new anti-C5 agent for patients with PNH and other complement-mediated disorders.

γ‐Glutamyltranspeptidase (GGT; EC 2.3.2.2), an enzyme found in organisms from bacteria to mammals and plants, plays a central role in glutathione metabolism. Structural studies of GGTs from Escherichia coli and Helicobacter pylori have revealed detailed molecular mechanisms of catalysis and maturation. In these two GGTs, highly conserved residues form the catalytic pockets, conferring the ability of the loop segment to shield the bound γ‐glutamyl moiety from the solvent. Here, we have examined the Bacillus subtilis GGT, which apparently lacks the amino acids corresponding to the lid‐loop that are present in mammalian and plant GGTs as well as in most bacterial GGTs. Another remarkable feature of B. subtilis GGT is its salt tolerance; it retains 86% of its activity even in 3 m NaCl. To better understand these characteristics of B. subtilis GGT, we determined its crystal structure in complex with glutamate, a product of the enzymatic reaction, at 1.95 Å resolution. This structure revealed that, unlike the E. coli and H. pylori GGTs, the catalytic pocket of B. subtilis GGT has no segment that covers the bound glutamate; consequently, the glutamate is exposed to solvent. Furthermore, calculation of the electrostatic potential showed that strong acidic patches were distributed on the surface of the B. subtilis GGT, even under high‐salt conditions, and this may allow the protein to remain in the hydrated state and avoid self‐aggregation. The structural findings presented here have implications for the molecular mechanism of GGT. Structured digital abstract  http://mint.bio.uniroma2.it/mint/search/interaction.do?interactionAc=MINT-7383558: GGT (uniprotkb:http://www.uniprot.org/uniprot/P54422?format=text&ascii) and GGT (uniprotkb:http://www.uniprot.org/uniprot/P54422?format=text&ascii) bind (http://www.ebi.ac.uk/ontology-lookup/?termId=MI:0407) by X‐ray crystallography (http://www.ebi.ac.uk/ontology-lookup/?termId=MI:0114)

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Impact ionization process in diamond under extremely high electric fields (EFs) has been investigated. The impact-ionization rate was calculated theoretically from Fermi's golden rule using the full band structure. It is found from Monte Carlo simulations that the impact ionization of carriers occurs at high EFs above 1×106 V/cm. The threshold EF for ionization is smaller for hole than for electron. Current(I)–voltage(V) characteristics measured for p-i-p diamond stacking structures revealed that I is approximately proportional to V 2 with substantial electroluminescence at EFs higher than 5×106 V/cm, being in good agreement with the theoretically predicted values.