Electrostatic Tuning of the Ligand Binding Mechanism by Glu27 in Nitrophorin 7

6533b7cffe1ef96bd1257cdd

RESEARCH PRODUCT

Electrostatic Tuning of the Ligand Binding Mechanism by Glu27 in Nitrophorin 7

Cristiano Viappiani F. Javier Luque Hideaki Ogata Hideaki Ogata Giancarlo Soavi Stefano Bruno Alessandro Allegri Axel Bidon-chanal Stefania Abbruzzetti Chiara Montali Giulio Cerullo

subject

Models Molecular 0301 basic medicine Conformational change Protein Conformation Molecular biology lcsh:Medicine Sang Crystallography X-Ray Ligands 01 natural sciences chemistry.chemical_compound Protein structure Models Zoologia Bloodsucking insects Nitrophorin Static electricity lcsh:Science Heme Cell receptors chemistry.chemical_classification Crystallography Multidisciplinary Parasitologia Amino acid Blood Rhodnius Insect Proteins Animals; Crystallography X-Ray; Glutamic Acid; Heme; Hemeproteins; Insect Proteins; Ligands; Models Molecular; Molecular Dynamics Simulation; Mutation; Protein Conformation; Rhodnius; Salivary Proteins and Peptides; Static Electricity Hemeproteins Hemeprotein Static Electricity Glutamic Acid Heme Molecular Dynamics Simulation 010402 general chemistry Article 03 medical and health sciences Animals Salivary Proteins and Peptides Biologia molecular Insectes hematòfags 030102 biochemistry & molecular biology lcsh:R Molecular 0104 chemical sciences Isoelectric point chemistry Mutation X-Ray Biophysics lcsh:Q Receptors cel·lulars Parasitology Zoology

description

AbstractNitrophorins (NP) 1–7 are NO-carrying heme proteins found in the saliva of the blood-sucking insect Rhodnius prolixus. The isoform NP7 displays peculiar properties, such as an abnormally high isoelectric point, the ability to bind negatively charged membranes, and a strong pH sensitivity of NO affinity. A unique trait of NP7 is the presence of Glu in position 27, which is occupied by Val in other NPs. Glu27 appears to be important for tuning the heme properties, but its influence on the pH-dependent NO release mechanism, which is assisted by a conformational change in the AB loop, remains unexplored. Here, in order to gain insight into the functional role of Glu27, we examine the effect of Glu27 → Val and Glu27 → Gln mutations on the ligand binding kinetics using CO as a model. The results reveal that annihilation of the negative charge of Glu27 upon mutation reduces the pH sensitivity of the ligand binding rate, a process that in turn depends on the ionization of Asp32. We propose that Glu27 exerts a through-space electrostatic action on Asp32, which shifts the pKa of the latter amino acid towards more acidic values thus reducing the pH sensitivity of the transition between open and closed states.

year	journal	country	edition	language
2018-07-01	Scientific Reports

https://doi.org/10.1038/s41598-018-29182-3