Biology subjects

Venkatraman, P.

Publications and source records attributed to Venkatraman, P..

3 recordsLinked to original sources

bioRxiv2021

Phosphorylation of interfacial phosphosite leads to increased binding of Rap-Raf complex

The effect of phosphorylation of a serine residue in the Rap protein, residing at the complex interface of Rap-Raf complex is studied using atomistic molecular dynamics simulations. As the phosphosite of interest (SER39) is buried at the interface of the Rap-Raf complex, phosphorylation of only Rap protein was simulated and then complexed with the RBD of Raf for further analysis of complex stability. Our simulations reveal that the phosophorylation increases the binding of complex through strong electrostatic interactions and changes the charge distribution of the interface significantly. This is manifested as an increase in stable salt-bridge interactions between the Rap and Raf of the complex. Network analysis clearly shows that the phosphorylation of SER39 reorganizes the community network to include the entire region of Raf chain, including, Raf L4 loop potentially affecting downstream signalling.

biophysics↗

bioRxiv2021

Structural insights on the effects of mutation of a charged binding pocket residue on phosphopeptide binding to 14-3-3 ζ Protein

Mutation of an invariant aspartate residue in the binding pocket of 14-3-3{zeta} isoform to alanine dramatically reduced phosphopeptide binding and induced opening of the binding pocket. Here we use extensive molecular dynamics simulations to understand the role of D124 residue in ligand binding. The simulations show that in the absence of phosphopeptide, the D124A mutation leads to binding pocket reorganization including widening up of the binding pocket at the major groove and repositioning of N173, a key residue that interacts with the main chain of phosphopeptide. These structural changes would interfere with the efficient binding of the peptide, corroborating the experimental observations. Both gain and loss of electrostatic interactions in the form of salt bridges strongly indicate a rearrangement of the network of interactions within the binding pocket. Limited proteolysis coupled mass spectrometry (lip-MS) of the apo and holo forms of WT and mutant protein shows a peptide binding helix otherwise buried in the WT protein was particularly accessible to trypsin in the apo form of the mutant protein and the region was mapped to 158-186 amino acid residues of 14-3-3{zeta}). These results further confirm the dynamic nature of D124A mutant. Unlike other basic residues, the invariant D124 facilitates peptide binding by maintaining the geometry of interacting residues and by enforcing the structural integrity of amphipathic pocket.

biophysics↗

bioRxiv2019

14-3-3γ prevents centrosome duplication by inhibiting NPM1 function.

14-3-3 proteins bind to ligands via phospho-Serine containing consensus motifs. However, the molecular mechanisms underlying complex formation and dissociation between 14-3-3 proteins and their ligands remain unclear. We identified two conserved acidic residues in the 14-3-3 peptide-binding pocket (D129 and E136) that potentially regulate complex formation and dissociation. Altering these residues to Alanine led to opposing effects on centrosome duplication. D129A inhibited centrosome duplication while E136A stimulated centrosome amplification. These results were due to the differing abilities of these mutant proteins to form a complex with NPM1. Inhibiting complex formation between NPM1 and 14-3-3{gamma} led to an increase in centrosome duplication and overrode the ability of D129A to inhibit centrosome duplication. We identify a novel role of 14-3-3 in regulating centrosome licensing and a novel mechanism underlying the formation and dissociation of 14-3-3 ligand complexes dictated by conserved residues in the 14-3-3 family.

cell biology↗