Mechanism of Action of Non-Synonymous Single Nucleotide Variations Associated with α-Carbonic Anhydrase II Deficiency.

Taremekedzwa Allan Sanyanga,Bilal Nizami,Özlem Tastan Bishop

doi:10.3390/molecules24213987

Abstract

Human carbonic anhydrase II (CA-II) is a Zinc (Zn) metalloenzyme responsible for maintenance of acid-base balance within the body through the reversible hydration of CO to produce protons (H) and bicarbonate (BCT). Due to its importance, alterations to the amino acid sequence of the protein as a result of single nucleotide variations (nsSNVs) have detrimental effects on homeostasis. Six pathogenic CA-II nsSNVs, K18E, K18Q, H107Y, P236H, P236R and N252D were identified, and variant protein models calculated using homology modeling. The effect of each nsSNV was analyzed using motif analysis, molecular dynamics (MD) simulations, principal component (PCA) and dynamic residue network (DRN) analysis. Motif analysis identified 11 functionally important motifs in CA-II. RMSD data indicated subtle SNV effects, while PCA analysis revealed that the presence of BCT results in greater conformational sampling and free energy in proteins. DRN analysis showed variant allosteric effects, and the average betweenness centrality (BC) calculations identified Glu117 as the most important residue for communication in CA-II. The presence of BCT was associated with a reduction to Glu117 usage in all variants, suggesting implications for Zn dissociation from the CA-II active site. In addition, reductions to Glu117 usage are associated with increases in the usage of the primary and secondary Zn ligands; His94, His96, His119 and Asn243 highlighting potential compensatory mechanisms to maintain Zn within the active site. Compared to traditional MD simulation investigation, DRN analysis provided greater insights into SNV mechanism of action, indicating its importance for the study of missense mutation effects in proteins and, in broader terms, precision medicine related research.

Highlights

Carbonic anhydrases (CAs) are metalloenzymes responsible for the catalysis of the reversible interconversion of carbon dioxide (CO2 ) and water (H2 O) to bicarbonate (HCO3− or BCT) and protons (H+ ), and the reaction is illustrated in Equation (1) [1,2]
The variants P236H and P236R are not located on any conserved motifs, whereas N252D is present on motif 3
Analysis of K18E contact maps in Figure 6 indicates no changes to interactions occurring between either Lys18 or Glu18 and the other protein residues; K18Q demonstrates that when BCT or CO2 are bound, Gln18 forms new interactions with His3

Summary

Introduction

Carbonic anhydrases (CAs) are metalloenzymes responsible for the catalysis of the reversible interconversion of carbon dioxide (CO2 ) and water (H2 O) to bicarbonate (HCO3− or BCT) and protons (H+ ), and the reaction is illustrated in Equation (1) [1,2]. CAs are Molecules 2019, 24, 3987; doi:10.3390/molecules24213987 www.mdpi.com/journal/molecules

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