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Volume 5, Issue 3(Suppl) Biochem Anal Biochem 2016
ISSN: 2161-1009, Biochem an open access journal
Page 47
Notes:
Biochemistry 2016
October 10-12, 2016
conferenceseries.com
Biochemistry
October 10-12, 2016 Kuala Lumpur, Malaysia
International Conference on
Crystal structure of substrate and AMPPNP bound propionate kinase from Salmonella typhimurium:
Substrate specificity and phosphate transfer mechanism
Subashini Mathivanan1, A M V Murthy 1,2, S Chittori1,3 , H S Savithri 2 and M R N Murthy1
1Indian Institute of Science Bangalore, India
2University of Queensland, Australia
3John Edward Porter Neuroscience Research Center, USA
Propionate kinase reversibly transfers phosphoryl group from propionyl phosphate to ADP in the final step of non-oxidative
catabolism of L-threonine to propionate. There are contrasting views on the phosphoryl transfer mechanism of propionate kinase.
Here we report X-ray crystal structures of propionate and nucleotide analog (AMPPNP) bound Salmonella typhimurium propionate
kinase at 1.8-2.2 Å resolutions. Although the mode of the nucleotide binding is comparable to those of other members of ASKHA
superfamily, propionate is bound at a distinct site, deeper in the hydrophobic pocket defining the active site. The role of Ala88, earlier
proposed to be the residue determining substrate specificity, was examined by determining the crystal structures of propionate bound
Ala88 mutants A88V and A88G. Kinetic analysis and structural data are consistent with a significant role of Ala88 in substrate
specificity determination. In the structure of StTdcD A88V-AMPPNP-Propionate complex, AMPPNP was cleaved to AMP and PNP
either due to an unreported catalytic activity of the enzyme or due to radiation damage. The released PNP probably reacted with
propionate forming propionyl-pyrophosphate, supporting direct in-line transfer mechanism. Phosphoryl transfer reaction is likely to
occur via an associative SN2-like transition state. The proximity of strictly conserved His175 and Arg236 to carboxyl of propionate
and γ-phosphate of ATP suggests their involvement in catalysis. Moreover, ligand binding does not induce global domain movement
as reported in some other members of ASKHA superfamily. However, the active site pocket defining residues Arg86, Asp143 and
Pro116-Leu117-His118 segment are also likely to contribute to substrate specificity.
Biography
Subashini Mathivanan is a PhD candidate at the Indian Institute of Science, Bangalore, India. Her research expertise is on protein crystallography, emphasized on structural
and functional characterization of Salmonella typhimurium propionate kinase and Photorhabdus luminescens oxalate decarboxylase.
Subashini Mathivanan et al., Biochem Anal Biochem 2016, 5:3(Suppl)