Structure and function of the Ts2631 endolysin of <i>Thermus scotoductus</i> phage vB_Tsc2631 with unique N-terminal extension used for peptidoglycan binding

Abstract To escape from hosts after completing their life cycle, bacteriophages often use endolysins, which degrade bacterial peptidoglycan. While mesophilic phages have been extensively studied, their thermophilic counterparts are not well characterized. Here, we present a detailed analysis of the structure and function of Ts2631 endolysin from thermophilic phage vB_Tsc2631, which is a zinc-dependent amidase. The active site of Ts2631 consists of His30, Tyr58, His131 and Cys139, which are involved in Zn2+ coordination and catalysis. We found that the active site residues are necessary for lysis yet not crucial for peptidoglycan binding. To elucidate residues involved in the enzyme interaction with peptidoglycan, we tested single-residue substitution variants and identified Tyr60 and Lys70 as essential residues. Moreover, substitution of Cys80, abrogating disulfide bridge formation, inactivates Ts2631, as do substitutions of His31, Thr32 and Asn85 residues. The endolysin contains a positively charged N-terminal extension of 20 residues that can protrude from the remainder of the enzyme and is crucial for peptidoglycan binding. We show that the deletion of 20 residues from the N-terminus abolished the bacteriolytic activity of the enzyme. Because Ts2631 exhibits intrinsic antibacterial activity and unusual thermal stability, it is perfectly suited as a scaffold for the development of antimicrobial agents

Crystal growth, structure and characterization of diglycine zinc dipicrate: Centrosymmetric crystal exhibiting second harmonic generation efficiency

<p></p> <p>Single crystals of diglycine zinc dipicrate (DZD) were grown by the slow evaporation solution growth technique from ethanol at room temperature. The structure is elucidated by single crystal XRD analysis and it belongs to the triclinic system with centrosymmetric space group P_ī. The crystallinity of the material was confirmed by powder X-ray diffraction analysis. The functional groups present in the molecule are identified by FT-IR analysis and the band gap energy is estimated using diffuse reflectance data by the application of Kubelka–Munk algorithm. Investigation of the intermolecular interactions and crystal packing <i>via</i> Hirshfeld surface analysis, based on single-crystal XRD, reveals the close contacts associated with molecular interactions. Fingerprint plots of the Hirshfeld surfaces were used to locate and analyze the percentage of hydrogen-bonding interactions.The data are analysed by combined results of single crystal XRD and electronic structure calculations. Theoretical calculations done by density functional theory(DFT) gives an idea about structure-function relationship. The second harmonic generation efficiency (SHG) is estimated using the Kurtz and Perry technique and it reveals second order nonlinearity. The observation of a centrosymmetric crystal exbiting NLO character is rationalized.</p