TY - JOUR T1 - A dimer between monomers and hexamers-Oligomeric variations in glucosamine-6-phosphate deaminase family. JF - PLoS One Y1 - 2023 A1 - Srinivasachari, Sathya A1 - Tiwari, Vikas R A1 - Kharbanda, Tripti A1 - Sowdamini, Ramanathan A1 - Subramanian, Ramaswamy KW - Aldose-Ketose Isomerases KW - Bacterial Proteins KW - Haemophilus influenzae KW - N-Acetylneuraminic Acid KW - Pasteurella multocida KW - Polymers AB -

In bacteria that live in hosts whose terminal sugar is a sialic acid, Glucosamine-6-phosphate deaminase (NagB) catalyzes the last step in converting sialic acid into Fructose-6-phosphate. These bacteria then use the Fructose-6-phosphate as an energy source. The enzyme NagB exists as a hexamer in Gram-negative bacteria and is allosterically regulated. In Gram-positive bacteria, it exists as a monomer and lacks allosteric regulation. Our identification of a dimeric Gram-negative bacterial NagB motivated us to characterize the structural basis of two closely related oligomeric forms. We report here the crystal structures of NagB from two Gram-negative pathogens, Haemophilus influenzae (Hi) and Pasturella multocida (Pm). The Hi-NagB is active as a hexamer, while Pm-NagB is active as a dimer. Both Hi-NagB and Pm-NagB contain the C-terminal helix implicated as essential for hexamer formation. The hexamer is described as a dimer of trimers. In the Pm-NagB dimer, the dimeric interface is conserved. The conservation of the dimer interface suggests that the three possible oligomeric forms of NagB are a monomer, a dimer, and a trimer of dimers. Computational modeling and MD simulations indicate that the residues at the trimeric interface have less stabilizing energy of oligomer formation than those in the dimer interface. We propose that Pm-NagB is the evolutionary link between the monomer and the hexamer forms.

VL - 18 IS - 1 ER - TY - JOUR T1 - Automation aided optimization of cloning, expression and purification of enzymes of the bacterial sialic acid catabolic and sialylation pathways enzymes for structural studies. JF - Microb Biotechnol Y1 - 2018 A1 - Bairy, Sneha A1 - Gopalan, Lakshmi Narayanan A1 - Setty, Thanuja Gangi A1 - Srinivasachari, Sathya A1 - Manjunath, Lavanyaa A1 - Kumar, Jay Prakash A1 - Guntupalli, Sai R A1 - Bose, Sucharita A1 - Nayak, Vinod A1 - Ghosh, Swagatha A1 - Sathyanarayanan, Nitish A1 - Caing-Carlsson, Rhawnie A1 - Wahlgren, Weixiao Yuan A1 - Friemann, Rosmarie A1 - Ramaswamy, S A1 - Neerathilingam, Muniasamy AB -

The process of obtaining a well-expressing, soluble and correctly folded constructs can be made easier and quicker by automating the optimization of cloning, expression and purification. While there are many semiautomated pipelines available for cloning, expression and purification, there is hardly any pipeline that involves complete automation. Here, we achieve complete automation of all the steps involved in cloning and in vivo expression screening. This is demonstrated using 18 genes involved in sialic acid catabolism and the surface sialylation pathway. Our main objective was to clone these genes into a His-tagged Gateway vector, followed by their small-scale expression optimization in vivo. The constructs that showed best soluble expression were then selected for purification studies and scaled up for crystallization studies. Our technique allowed us to quickly find conditions for producing significant quantities of soluble proteins in Escherichia coli, their large-scale purification and successful crystallization of a number of these proteins. The method can be implemented in other cases where one needs to screen a large number of constructs, clones and expression vectors for successful recombinant production of functional proteins.

VL - 11 IS - 2 ER -