Biology subjects

Reddy, C. N.

Publications and source records attributed to Reddy, C. N..

2 recordsLinked to original sources

bioRxiv2022

Dissociation of CED-4 from CED-9 upon EGL-1 binding: Molecular mechanism of linear apoptotic pathway in Caenorhabditis elegans

Many steps in programmed cell death are evolutionarily conserved across different species. The Caenorhabditis elegans proteins CED-9, CED-4 and EGL-1 involved in apoptosis are respectively homologous to anti-apoptotic Bcl-2 proteins, Apaf-1 and the "BH3-only" pro- apototic proteins in mammals. In the linear apoptotic pathway of C.elegans, EGL-1 binding to CED-9 leads to the release of CED-4 from CED-9/CED-4 complex. The molecular events leading to this process are not clearly elucidated. While the structures of CED-9 apo, CED- 9/EGL-1 and CED-9/CED-4 complexes are known, the CED-9/CED-4/EGL-1 ternary complex structure is not yet determined. In this work, we modeled this ternary complex and performed molecular dynamics simulations of six different systems involving CED-9. CED-9 displays differential dynamics depending upon whether it is bound to CED-4 and/or EGL-1. CED-4 exists as an asymmetric dimer (CED4a and CED4b) in CED-9/CED-4 complex. CED-4a exhibits higher conformational flexibility when simulated without CED-4b. Principal Component Analysis revealed that the direction of CED-4as winged-helix domain motion differs in the ternary complex. Upon EGL-1 binding, majority of non-covalent interactions involving CARD domain in the CED-4a-CED-9 interface have weakened and only half of the contacts found in the crystal structure between /{beta} domain of CED4a and CED-9 are found to be stable. Additional stable contacts in the ternary complex and differential dynamics indicate that winged-helix domain may play a role in CED-4as dissociation from CED-9. This study has provided a molecular level understanding of potential intermediate states that are likely to occur at the time of CED-4as release from CED-9.

biophysics↗

bioRxiv2021

Designing BH3-mimetic Peptide Inhibitors for the Viral Bcl-2 Homologs A179L and BHRF1: Importance of long-range electrostatic interactions

Viruses have evolved strategies to prevent apoptosis of infected cells at early stages of infection. The viral proteins (vBcl-2s) from specific viral genes adopt a helical fold that is structurally similar to that of mammalian anti-apoptotic Bcl-2 proteins and exhibit little sequence similarity. Hence vBcl-2 homologs are attractive targets to prevent viral infection. However, very few studies have focused on developing inhibitors for vBcl-2 homologs. In this study, we have considered two vBcl-2 homologs, A179L from African swine fever virus and BHRF1 from Epstein-Barr virus. We generated two sets of 8000 randomized BH3-like sequences from eight wild-type pro-apoptotic BH3 peptides. During this process, the four conserved hydrophobic residues and an Asp residue were retained at their respective positions and all other positions were substituted randomly without any bias. We constructed 8000 structures each for A179L and BHRF1 in complex with BH3-like sequences. Histograms of interaction energies calculated between the peptide and the protein resulted in negatively skewed distributions. The BH3-like peptides with high helical propensities selected from the negative tail of respective interaction energy distributions exhibited more favorable interactions with A179L and BHRF1 and they are rich in basic residues. Molecular dynamics studies and electrostatic potential maps further revealed that both acidic and basic residues favorably interact with A179L while only basic residues have the most favorable interactions with BHRF1. As in mammalian homologs, the role of long range interactions and non-hotspot residues have to be taken into account while designing specific BH3-mimetic inhibitors for vBcl-2 homologs.

biophysics↗