One fold, two functions: cytochrome P460 and cytochrome c′-β from the methanotroph Methylococcus capsulatus (Bath)

Nature is adept at utilising highly similar protein folds to carry out very different functions, yet the mechanisms by which this functional divergence occurs remain poorly characterised. In certain methanotrophic bacteria, two homologous pentacoordinate c-type heme proteins have been identified: a cytochrome P460 (cyt P460) and a cytochrome c′-β (cyt cp-β). Cytochromes P460 are able to convert hydroxylamine to nitrous oxide (N2O), a potent greenhouse gas. This reactivity is similar to that of hydroxylamine oxidoreductase (HAO), which is a key enzyme in nitrifying and methanotrophic bacteria. Cyt P460 and HAO both have unusual protein-heme cross-links, formed by a Tyr residue in HAO and a Lys in cyt P460. In contrast, cyts cp-β (the only known cytochromes c′ with a β-sheet fold) lack this crosslink and appears to be optimized for binding non-polar molecules (including NO and CO) without enzymatic conversion. Our bioinformatics analysis supports the proposal that cyt cp-β may have evolved from cyt P460 via a gene duplication event. Using high-resolution X-ray crystallography, UV-visible absorption, electron paramagnetic resonance (EPR) and resonance Raman spectroscopy, we have characterized the overall protein folding and active site structures of cyt cp-β and cyt P460 from the obligate methanotroph, Methylococcus capsulatus (Bath). These proteins display a similar β-sheet protein fold, together with a pattern of changes to the heme pocket regions and localised tertiary structure that have converted a hydroxylamine oxidizing enzyme into a gas-binding protein. Structural comparisons provide insights relevant to enzyme redesign for synthetic enzymology and engineering of gas sensor proteins. We also show the widespread occurrence of cyts cp-β and characterise their phylogeny

Dissecting the physiology and pathophysiology of glucagon-like peptide-1

Copyright © 2018 Paternoster and Falasca. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms. An aging world population exposed to a sedentary life style is currently plagued by chronic metabolic diseases, such as type-2 diabetes, that are spreading worldwide at an unprecedented rate. One of the most promising pharmacological approaches for the management of type 2 diabetes takes advantage of the peptide hormone glucagon-like peptide-1 (GLP-1) under the form of protease resistant mimetics, and DPP-IV inhibitors. Despite the improved quality of life, long-term treatments with these new classes of drugs are riddled with serious and life-threatening side-effects, with no overall cure of the disease. New evidence is shedding more light over the complex physiology of GLP-1 in health and metabolic diseases. Herein, we discuss the most recent advancements in the biology of gut receptors known to induce the secretion of GLP-1, to bridge the multiple gaps into our understanding of its physiology and pathology

Omnidirectional Free-viewpoint Rendering Using a Deformable 3-D Mesh Model

This paper proposes a method to render free viewpoint images from omnidirectional videos using a deformable 3-D mesh model. In the proposed method, a 3-D mesh is placed in front of a virtual viewpoint and deformed by using the pre-estimated omnidirectional depth maps that are selected on the basis of position and posture of the virtual viewpoint. Although our approach is fundamentally based on the model-based rendering approach that renders a geometrically correct virtualized world, in order to avoid the hole problem, we newly employ a viewpoint-dependent deformable 3-D model instead of the use of a unified 3-D model that is generally used in the model based rendering approach. In experiments, free-viewpoint images are generated from the omnidirectional video captured by an omnidirectional multi camera system to show the feasibility of the proposed method for walk-through applications in the virtualized environment

Omnidirectional Free-viewpoint Rendering Using a Deformable 3-D Mesh Model

International audienceThis paper proposes a method to render free viewpoint images from omnidirectional videos using a deformable 3-D mesh model. In the proposed method, a 3-D mesh is placed in front of a virtual viewpoint and deformed by using the pre-estimated omnidirectional depth maps that are selected on the basis of position and posture of the virtual viewpoint. Although our approach is fundamentally based on the model-based rendering approach that renders a geometrically correct virtualized world, in order to avoid the hole problem, we newly employ a viewpoint-dependent deformable 3-D model instead of the use of a unified 3-D model that is generally used in the model based rendering approach. In experiments, free-viewpoint images are generated from the omnidirectional video captured by an omnidirectional multi camera system to show the feasibility of the proposed method for walk-through applications in the virtualized environment