Water molecule-mediated selective inhibition of bacterial zinc metalloproteinases by non-hydroxamate compounds: Ab initio molecular simulations.

UDP-3-O-acyl-N acetylglucosamine deacetylase (LpxC), Zn metalloenzyme for Gram-negative bacteria is an attractive target for developing novel therapeutic agents. Since LpxC has the similar binding pocket as the human matrix metalloproteinases (MMPs), LpxC inhibitors might also inhibit MMP functions producing side effects in human bodies. Here, we investigated specific interactions between LpxC/MMP and their inhibitors using ab initio molecular simulations to elucidate the reason of selective inhibition for LpxC by non-hydroxamate compounds. The evaluated binding properties between LpxC and the compounds are comparable to the trend of their observed inhibitory affinities. It was also elucidated that compound 22 binds most strongly to LpxC due to its specific interactions with Zn ion and Asp241 side chain of LpxC. In contrast, the interactions between the compounds and MMP are significantly weakened due to the water molecules, which are tightly coordinated with the Zn ion in MMP and interrupt the binding of the compounds to the Zn ion. Accordingly, the present molecular simulations revealed that these water molecules around the Zn ion in MMP are causally related to the selective inhibition of these compounds for LpxC rather than MMP.

Proposal of selective inhibitor for bacterial zinc metalloprotease: Molecular mechanics and ab initio molecular orbital calculations.

The zinc metalloprotease pseudolysin (PLN) secreted from Pseudomonas aeruginosa degrades extracellular proteins to produce bacterial nutrition, and various types of PLN inhibitors have been developed to suppress the bacterial growth. However, as the structure of the ligand-binding pocket of PLN has large similarities to those of human matrix metalloproteinases (MMPs) and other human zinc metalloprotease, there is a risk that PLN inhibitors also inhibit human zinc proteases. In this study, we propose a novel agent that may bind stronger to PLN than to MMPs. The compound is proposed based on the specific molecular interactions between existing agents and PLN/MMP metalloproteases evaluated by the present molecular simulations. First, we confirmed that the binding energies of PLN agents evaluated using the ab initio fragment molecular orbital method were comparable to the IC50 values obtained through previous experiments. In addition, the specific molecular interactions between these agents and MMP-9 were investigated to elucidate the fact that some of the agents bind weaker to MMP than PLN. Based on the results, we proposed a novel agent having a succinimide group introduce by a hydroxamic acid group and investigated its binding properties with PLN and MMP. The results may provide useful information for the development of potent inhibitors for PLN with few potential side effects in human bodies.

Specific interactions between the alkaline protease of P. aeruginosa and its natural peptide inhibitor: ab initio molecular simulations.

Alkaline protease aeruginolysin (APR) is an important virulence factor in the evasion of the immune system by Pseudomonas aeruginosa (P. aeruginosa). The P. aeruginosa genome also encodes the highly potent and specific APR peptide inhibitor (APRin). However, the structural reason for the significant inhibition has not been revealed. Using ab initio molecular simulations, we here investigated the specific interactions between APR and APRin to elucidate which amino acid residues of APRin and APR contribute strongest to the inhibition. Since APR has a Zn2+ ion at the ligand-binding site and histidine and glutamic acid residues are coordinated with Zn2+, it is essential to precisely describe these coordination bonds to elucidate the specific interactions between APR and APRin. Therefore, we employed the ab initio fragment molecular orbital method to investigate the specific interactions at an electronic level. The results revealed that Ser1 and Ser2 at the N-terminus of APRin significantly contribute to the binding between APRin and APR. In particular, Ser1 binds strongly to Zn2+ as well as to the sidechains of His176(Hid), His180(Hid), and His186(Hid) in APR. This is the main reason for the strong interaction between APR and APRin. The results also elucidated significant contributions of the positively charged Arg83 and Arg90 residues of APRin to the binding with APR. These findings may provide information useful for the design of novel small agents as potent APR inhibitors.

Protonation states of central amino acids in a zinc metalloprotease complexed with inhibitor: Molecular mechanics optimizations and ab initio molecular orbital calculations.

The zinc-metalloprotease pseudolysin (PLN) secreted from bacteria degrades extracellular proteins to produce bacterial nutrition. Since PLN has a Zn ion at the inhibitor-binding site, the interactions between Zn and PLN residues as well as inhibitor can be significantly changed depending on the protonation states of PLN residues at the inhibitor-binding site. To determine stable protonation states of these residues, we here considered different protonation states for Glu and His residues located around Zn and investigated the electronic states of the PLN + inhibitor complex, using ab initio molecular simulations. The protonation state of His223 was found to significantly affect the specific interactions between PLN and the inhibitor.

Design of galardine analogs as putative psudolysin inhibitors based on ab initio fragment molecular orbital calculations.

Pseudolysin (PLN) is a metalloproteinase secreted from bacteria that degrades extracellular proteins to produce bacterial nutrition. It is thus expected that inhibitors against PLN can suppress the growth of bacteria and their pandemic spread. In addition, since these inhibitors do not attack to bacteria directly, there is a reduced risk for producing drug-resistant bacteria. On the other hand, as PLN has large structural similarity in the active sites with human matrix-metalloproteinases (MMPs), there is a possibility that the inhibitors for PLN also inhibit MMP activity, resulting in a loss of necessary nutrients to be produced by MMPs. Therefore, it is required the agents inhibiting the activity of only PLN not MMPs. In the present study, we employed a hydroxamate compound galardin, which has a significant inhibition effect against PLN and MMP, and investigated its specific interactions with PLN/MMP at atomic and electronic levels, by use of ab initio molecular simulations. Based on the results, we proposed several derivatives of galardin and elucidated which derivatives that can bind more strongly to PLN and be putative antimicrobial agents capable of inhibiting the PLN activity.Communicated by Ramaswamy H. Sarma.

Specific interactions between 2-trans enoyl-acyl carrier protein reductase and its ligand: Protein-ligand docking and ab initio fragment molecular orbital calculations.

2-trans enoyl-acyl carrier protein reductase (InhA) has been identified as a promising target for the development of novel chemotherapy for tuberculosis. In the present study, a series of heteroaryl benzamide derivatives were selected as potent inhibitors against InhA, and their binding properties with InhA were investigated at atomic and electronic levels by ab initio molecular simulations based on protein-ligand docking, classical molecular mechanics optimizations and ab initio fragment molecular orbital (FMO) calculations. The results evaluated by FMO highlight some key interactions between InhA and the derivatives, indicating that the most potent derivative has strong hydrogen bonds with the Met98 side chain of InhA and strong electrostatic interactions with the nicotinamide adenine dinucleotide cofactor. These findings provide informative structural concepts for designing novel heteroaryl benzamide derivatives with higher binding affinity to InhA.