Comparative Modeling And Enzymatic Affinity of Novel Haloacid Dehalogenase From Bacillus Megaterium Strain BHS1 Isolated From Alkaline Blue Lake In Turkey

This is the first structural model of L-haloacid dehalogenase (DehLBHS1) isolated from alkalotolerant Bacillus megaterium BHS1, which has been known to degrading halogenated environmental contaminants. The study suggested five important key amino acid residues of DehLBHS1, namely Arg40, Phe59, Asn118, Asn176 and Trp178 important for catalysis and molecular recognition of haloalkanoic acid. Alkatolerant DehLBHS1was modeled by I-TASSER with the best C-score 1.23. Model validation was carried out utilising PROCHECK to produce the Ramachandran map with 89.2 percent of its residues were found in the most preferred region, indicating that the model was appropriate. The Molecular docking (MD) simulation found that the DehLBHS1 preferred 2,2DCP more than other substrates and formed one hydrogen bond with Arg40 and minimum energy -2.5 kJ/ mol. Molecular dynamics has verified the substrate preference towards 2,2DCP based on RMSD, RMSF, Gyration, Hydrogen bond and Molecular distance. This structural knowledge from DehLBHS1 structural perspective gives insights into substrate specificity and catalytic function to exploit DehLBHS1 of BHS1 strain in degrading 2,2-DCP in the polluted alkaline environments.

Limitations of the ABEGO representation: ambiguity between αα-corner and αα-hairpin

SummaryABEGO is a coarse-grained representation for polypeptide backbone dihedral angles. The Ramachandran map is divided into four segments denoted as A, B, E, and G to represent the local conformation of polypeptide chains in the character strings. Although the ABEGO representation is widely used in structural informatics and protein design, it cannot capture minor differences in backbone dihedral angles, which potentially leads to ambiguity between two structurally distinct fragments. Here, we show a nontrivial example of two local motifs that could not be distinguished by their ABEGO representations. We found that two well-known local motifs αα-hairpins and αα-corners are both represented as α-GBB-α and thus indistinguishable in the ABEGO representation, although they show distinct arrangements of the flanking α-helices. We also found that α-GBB-α motifs caused a loss of efficiency in the ABEGO-based fragment-assembly simulations for protein backbone design. Nevertheless, we designed amino-acid sequences that were predicted to fold into the target topologies that contained these α-GBB-α motifs. Our finding that certain local motifs bottleneck the ABEGO-based fragment-assembly simulations for construction of backbone structures suggests that finer representations of backbone torsion angles are required for efficiently generating diverse topologies containing such indistinguishable local motifs.

THE RAMACHANDRAN MAP OF MORE THAN 6,500 PERFECT POLYPEPTIDE CHAINS

The Protein Data Bank (PDB) is the most important depository of protein structural information, containing more than 45,000 deposited entries today. Because of its inhomogeneous structure, its fully automated processing is almost impossible. In a previous work, we cleaned and re-structured the entries in the Protein Data Bank, and from the result we have built the RS-PDB database. Using the RS-PDB database, we draw a Ramachandran-plot from 6,593 "perfect" polypeptide chains found in the PDB, containing 1,192,689 residues. This is a more than tenfold increase in the size of data analyzed before this work. The density of the data points makes it possible to draw a logarithmic heat map enhanced Ramachandran map, showing the fine inner structure of the right-handed α-helix region.