Structural Impacts of Drug-Resistance Mutations Appearing in HIV-2 Protease.

The use of antiretroviral drugs is accompanied by the emergence of HIV-2 resistances. Thus, it is important to elucidate the mechanisms of resistance to antiretroviral drugs. Here, we propose a structural analysis of 31 drug-resistant mutants of HIV-2 protease (PR2) that is an important target against HIV-2 infection.

Impacts of drug resistance mutations on the structural asymmetry of the HIV-2 protease.

Background: Drug resistance is a severe problem in HIV treatment. HIV protease is a common target for the design of new drugs for treating HIV infection. Previous studies have shown that the crystallographic structures of the HIV-2 protease (PR2) in bound and unbound forms exhibit structural asymmetry that is important for ligand recognition and binding.

Exploration of the effects of sequence variations between HIV-1 and HIV-2 proteases on their three-dimensional structures.

HIV protease inhibitors (PIs) approved by the FDA (US Food and Drug Administration) are a major class of antiretroviral. HIV-2 protease (PR2) is naturally resistant to most of them as PIs were designed for HIV-1 protease (PR1). In this study, we explored the impact of amino-acid substitutions between PR1 and PR2 on the structure of protease (PR) by comparing the structural variability of 13 regions using 24 PR1 and PR2 structures complexed with diverse ligands.

High Impact: The Role of Promiscuous Binding Sites in Polypharmacology.

The literature focuses on drug promiscuity, which is a drug's ability to bind to several targets, because it plays an essential role in polypharmacology. However, little work has been completed regarding binding site promiscuity, even though its properties are now recognized among the key factors that impact drug promiscuity. Here, we quantified and characterized the promiscuity of druggable binding sites from protein-ligand complexes in the high quality Mother Of All Databases while using statistical methods.

HIV-1 protease, Gag and gp41 baseline substitutions associated with virological response to a PI-based regimen.

Objectives: To assess, at ART initiation, the impact of baseline substitutions in protease, Gag and gp41 regions on the virological response to a first-line PI-based regimen.

Patients And Methods: One hundred and fifty-four HIV-infected ART-naive patients initiating a PI-based regimen including darunavir (n = 129) or atazanavir (n = 25) were assessed, including 36 experiencing virological failure (VF). Whole pol, gag and gp41 genes were sequenced at ART baseline by ultra-deep sequencing (UDS) using Illumina® technology.

Characterizing the structural variability of HIV-2 protease upon the binding of diverse ligands using a structural alphabet approach.

The HIV-2 protease (PR2) is an important target for designing new drugs against the HIV-2 infection. In this study, we explored the structural backbone variability of all available PR2 structures complexed with various inhibitors using a structural alphabet approach. 77% of PR2 positions are structurally variable, meaning they exhibit different local conformations in PR2 structures.

SAFlex: A structural alphabet extension to integrate protein structural flexibility and missing data information.

In this paper, we describe SAFlex (Structural Alphabet Flexibility), an extension of an existing structural alphabet (HMM-SA), to better explore increasing protein three dimensional structure information by encoding conformations of proteins in case of missing residues or uncertainties. An SA aims to reduce three dimensional conformations of proteins as well as their analysis and comparison complexity by simplifying any conformation in a series of structural letters. Our methodology presents several novelties.

Exploration of the effect of sequence variations located inside the binding pocket of HIV-1 and HIV-2 proteases.

HIV-2 protease (PR2) is naturally resistant to most FDA (Food and Drug Administration)-approved HIV-1 protease inhibitors (PIs), a major antiretroviral class. In this study, we compared the PR1 and PR2 binding pockets extracted from structures complexed with 12 ligands. The comparison of PR1 and PR2 pocket properties showed that bound PR2 pockets were more hydrophobic with more oxygen atoms and fewer nitrogen atoms than PR1 pockets.

Analysis of the HIV-2 protease's adaptation to various ligands: characterization of backbone asymmetry using a structural alphabet.

The HIV-2 protease (PR2) is a homodimer of 99 residues with asymmetric assembly and binding various ligands. We propose an exhaustive study of the local structural asymmetry between the two monomers of all available PR2 structures complexed with various inhibitors using a structural alphabet approach. On average, PR2 exhibits asymmetry in 31% of its positions-i.

Exploring the potential of a structural alphabet-based tool for mining multiple target conformations and target flexibility insight.

Protein flexibility is often implied in binding with different partners and is essential for protein function. The growing number of macromolecular structures in the Protein Data Bank entries and their redundancy has become a major source of structural knowledge of the protein universe. The analysis of structural variability through available redundant structures of a target, called multiple target conformations (MTC), obtained using experimental or modeling methods and under different biological conditions or different sources is one way to explore protein flexibility.

Statistical Profiling of One Promiscuous Protein Binding Site: Illustrated by Urokinase Catalytic Domain.

While recent literature focuses on drug promiscuity, the characterization of promiscuous binding sites (ability to bind several ligands) remains to be explored. Here, we present a proteochemometric modeling approach to analyze diverse ligands and corresponding multiple binding sub-pockets associated with one promiscuous binding site to characterize protein-ligand recognition. We analyze both geometrical and physicochemical profile correspondences.

Cavity Versus Ligand Shape Descriptors: Application to Urokinase Binding Pockets.

We analyzed 78 binding pockets of the human urokinase plasminogen activator (uPA) catalytic domain extracted from a data set of crystallized uPA-ligand complexes. These binding pockets were computed with an original geometric method that does NOT involve any arbitrary parameter, such as cutoff distances, angles, and so on. We measured the deviation from convexity of each pocket shape with the pocket convexity index (PCI).

Investigating the Importance of the Pocket-estimation Method in Pocket-based Approaches: An Illustration Using Pocket-ligand Classification.

Small molecules interact with their protein target on surface cavities known as binding pockets. Pocket-based approaches are very useful in all of the phases of drug design. Their first step is estimating the binding pocket based on protein structure.

Structural Isosteres of Phosphate Groups in the Protein Data Bank.

We developed a computational workflow to mine the Protein Data Bank for isosteric replacements that exist in different binding site environments but have not necessarily been identified and exploited in compound design. Taking phosphate groups as examples, the workflow was used to construct 157 data sets, each composed of a reference protein complexed with AMP, ADP, ATP, or pyrophosphate as well other ligands. Phosphate binding sites appear to have a high hydration content and large size, resulting in U-shaped bioactive conformations recurrently found across unrelated protein families.

PockDrug-Server: a new web server for predicting pocket druggability on holo and apo proteins.

Predicting protein pocket's ability to bind drug-like molecules with high affinity, i.e. druggability, is of major interest in the target identification phase of drug discovery.

PockDrug: A Model for Predicting Pocket Druggability That Overcomes Pocket Estimation Uncertainties.

Predicting protein druggability is a key interest in the target identification phase of drug discovery. Here, we assess the pocket estimation methods' influence on druggability predictions by comparing statistical models constructed from pockets estimated using different pocket estimation methods: a proximity of either 4 or 5.5 Å to a cocrystallized ligand or DoGSite and fpocket estimation methods.

Structure of the prolyl-acyl carrier protein oxidase involved in the biosynthesis of the cyanotoxin anatoxin-a.

Anatoxin-a and homoanatoxin-a are two potent cyanobacterial neurotoxins biosynthesized from L-proline by a short pathway involving polyketide synthases. Proline is first loaded onto AnaD, an acyl carrier protein, and prolyl-AnaD is then oxidized to 1-pyrroline-5-carboxyl-AnaD by a flavoprotein, AnaB. Three polyketide synthases then transform this imine into anatoxin-a or homoanatoxin-a.

Insights into an original pocket-ligand pair classification: a promising tool for ligand profile prediction.

Pockets are today at the cornerstones of modern drug discovery projects and at the crossroad of several research fields, from structural biology to mathematical modeling. Being able to predict if a small molecule could bind to one or more protein targets or if a protein could bind to some given ligands is very useful for drug discovery endeavors, anticipation of binding to off- and anti-targets. To date, several studies explore such questions from chemogenomic approach to reverse docking methods.

Characterization of Arabidopsis calcium-dependent protein kinases: activated or not by calcium?

CDPKs (calcium-dependent protein kinases), which contain both calmodulin-like calcium binding and serine/threonine protein kinase domains, are only present in plants and some protozoans. Upon activation by a stimulus, they transduce the signal through phosphorylation cascades to induce downstream responses, including transcriptional regulation. To understand the functional specificities of CDPKs, 14 Arabidopsis CPKs (CDPKs in plants) representative of the three main subgroups were characterized at the biochemical level, using HA (haemagglutinin)-tagged CPKs expressed in planta.

Dissecting protein loops with a statistical scalpel suggests a functional implication of some structural motifs.

Background: One of the strategies for protein function annotation is to search particular structural motifs that are known to be shared by proteins with a given function.

Results: Here, we present a systematic extraction of structural motifs of seven residues from protein loops and we explore their correspondence with functional sites. Our approach is based on the structural alphabet HMM-SA (Hidden Markov Model - Structural Alphabet), which allows simplification of protein structures into uni-dimensional sequences, and advanced pattern statistics adapted to short sequences.

SA-Mot: a web server for the identification of motifs of interest extracted from protein loops.

The detection of functional motifs is an important step for the determination of protein functions. We present here a new web server SA-Mot (Structural Alphabet Motif) for the extraction and location of structural motifs of interest from protein loops. Contrary to other methods, SA-Mot does not focus only on functional motifs, but it extracts recurrent and conserved structural motifs involved in structural redundancy of loops.

Exact distribution of a pattern in a set of random sequences generated by a Markov source: applications to biological data.

Background: In bioinformatics it is common to search for a pattern of interest in a potentially large set of rather short sequences (upstream gene regions, proteins, exons, etc.). Although many methodological approaches allow practitioners to compute the distribution of a pattern count in a random sequence generated by a Markov source, no specific developments have taken into account the counting of occurrences in a set of independent sequences.

Mining protein loops using a structural alphabet and statistical exceptionality.

Background: Protein loops encompass 50% of protein residues in available three-dimensional structures. These regions are often involved in protein functions, e.g.

Taking advantage of local structure descriptors to analyze interresidue contacts in protein structures and protein complexes.

Interresidue protein contacts in proteins structures and at protein-protein interface are classically described by the amino acid types of interacting residues and the local structural context of the contact, if any, is described using secondary structures. In this study, we present an alternate analysis of interresidue contact using local structures defined by the structural alphabet introduced by Camproux et al. This structural alphabet allows to describe a 3D structure as a sequence of prototype fragments called structural letters, of 27 different types.