Novel protein–protein interaction between spermidine synthase and S-adenosylmethionine decarboxylase from Leishmania donovani

•L. donovani spermidine synthase and S-adenosylmethionine decarboxylase have been cloned and purified.•S-adenosylmethionine decarboxylase has autocatalytic property.•GST pull down assay shows the two proteins to form a metabolon.•Isothermal titration calorimetry shows that binding was exothermic having Kd value of 0.4 μM.•Interaction confirmed by fluorescence spectroscopy and size exclusion chromatography.

Polyamine biosynthesis pathway has long been considered an essential drug target for trypanosomatids including Leishmania. S-adenosylmethionine decarboxylase (AdoMetDc) and spermidine synthase (SpdSyn) are enzymes of this pathway that catalyze successive steps, with the product of the former, decarboxylated S-adenosylmethionine (dcSAM), acting as an aminopropyl donor for the latter enzyme. Here we have explored the possibility of and identified the protein–protein interaction between SpdSyn and AdoMetDc. The protein–protein interaction has been identified using GST pull down assay. Isothermal titration calorimetry reveals that the interaction is thermodynamically favorable. Fluorescence spectroscopy studies also confirms the interaction, with SpdSyn exhibiting a change in tertiary structure with increasing concentrations of AdoMetDc. Size exclusion chromatography suggests the presence of the complex as a hetero-oligomer. Taken together, these results suggest that the enzymes indeed form a heteromer. Computational analyses suggest that this complex differs significantly from the corresponding human complex, implying that this complex could be a better therapeutic target than the individual enzymes.