Dr. Rajendra P. Roy

Research Interest:

Our laboratory is engaged in researches at the interface of chemistry and biology. We are interested in developing chemoenzymatic strategies for semisynthesis of proteins and bio-conjugates by combining enzymatic peptide ligation with chemical peptide synthesis, organic synthesis and recombinant protein expression.

Key words: Chemical biology, Synthetic protein chemistry, Peptide ligation, Protein engineering, Sortase

Summary of Research:

In the past we have addressed mechanistic aspects of peptide ligation reactions catalyzed by proteases. We have elaborated the concept of product-specific traps as a mechanism to facilitate reverse proteolytic condensation of polypeptide fragments. Furthermore, we have established volume exclusion effect, emanating from macromolecular crowding or confinement, as a driving force for reverse proteolysis.

Current work in our laboratory is focused on elucidating the amide bond forming specificity of bacterial transpeptidase (referred to as sortases). Sortases are cysteine transpeptidases that anchor surface proteins to the cell wall in Gram-positive bacteria. The archetypal sortase (SrtA) of Staphylococcus aureus recognizes a pentapeptide LPXTG motif present near the carboxy terminus of surface proteins, cleaves the T-G peptide bond and ligates the Protein-LPXT to the aminoglycine of the pentaglycine sequence present in peptidoglycan leading to anchoring of proteins to the cell wall.

SrtA-mediated peptide ligation reaction also proceeds well with short LPXTG peptides and aminoglycine terminated sequences. The propensity of SrtA to recognize short consensus sequences has inspired the use of this enzyme as a versatile synthetic tool in protein chemistry and chemical biology. Several applications of SrtA including introduction of novel functionality (viz., fluorescent labels, lipids, GPI anchors etc) into proteins, generation of circular proteins and surface immobilization of proteins have emerged in the past 7-8 years.  Contemporaneously, we have been engaged in exploring the utility of SrtA in the synthesis of glycoconjugates, cyclic peptides, branched peptide oligomers and multivalent protein dendrimers that are not amenable to synthesis by purely chemical or genetic means.

Group Members:
Vijay S Pawale, Prity Yadav, Avinash Kumar Singh, Shagun Shukla, Sumit Murmu

Awards:
• The J.C. Bose National Fellowship
• Fellow of Indian National Science Academy
• Fellow of National Academy of Sciences, India
• Fellow of The Indian Academy of Sciences
• Member of Guha Research Conference
• National Bioscience Award for Career Development (DBT, Govt of India)
• Biotechnology Overseas Associateship (DBT, Govt of India)
• Ella Fitzgerald Fellowship (New York Heart Association, USA)