Structural and functional studies of the Leishmania braziliensis mitochondrial Hsp70: Similarities and dissimilarities to human orthologues

Heat shock protein 70 kDa (Hsp70) is a conserved molecular chaperone family involved in several functions related to protein homeostasis. In eukaryotes, Hsp70 homologues are found in all cell compartments. The mitochondrial Hsp70 isoform (mtHsp70) is involved in import of mitochondrial matrix proteins as well as their folding and maturation. Moreover, mtHsp70 has the propensity to self-aggregate, and it depends on the action of the co-chaperone Hsp70-escort protein 1 (Hep1) to be produced functional. Here, we analyze the solution structure and function of mtHsp70 of Leishmania braziliensis (LbmtHsp70). This recombinant protein was obtained folded, in the monomeric state and it has an elongated shape. We observed that LbmtHsp70 suffers thermal aggregation that depends on the protein concentration and is composed of domains with different thermal stabilities. LbmtHsp70 interacted with adenosine nucleotides with a thermodynamic signature different from those reported for human orthologues and interacted, driven by both enthalpy and entropy, with L. braziliensis Hep1 (LbHep1) with a nanomolar dissociation constant. Moreover, LbHep1 stimulated the LbmtHsp70 ATPase activity. Since little is known about mitochondrial Hsp70, particularly in protozoa, we believe that our data are of interest for understanding protozoan Hsp70 machinery.