Low Resolution Structural Studies Indicate that the Activator of Hsp90 ATPase 1 (Aha1) of Leishmania braziliensis Has an Elongated Shape Which Allows Its Interaction with Both N- and M-Domains of Hsp90

Author(s)

Seraphim, Thiago V. ^{[1, 2]} ; Alves, Marina M. ^[1] ; Silva, Indjara M. ^[1] ; Gomes, Francisco E. R. ^[1] ; Silva, Kelly P. ^[1] ; Murta, Silvane M. F. ^[3] ; Barbosa, Leandro R. S. ^[4] ; Borges, Julio C. ^[1]

Affiliation

^[1] Univ Sao Paulo, Inst Quim Sao Carlos, Sao Carlos, SP - Brazil

^[2] Univ Fed Sao Carlos, Ctr Ciencias Biol & Saude, BR-13560 Sao Carlos, SP - Brazil

^[3] Ctr Pesquisa Rene Rachou, Belo Horizonte, MG - Brazil

^[4] Univ Sao Paulo, Inst Fis, Dept Fis Geral, Sao Carlos, SP - Brazil

• Document type: Journal article
• Source: PLoS One; v. 8, n. 6 JUN 24 2013.
• Web of Science Citations: 13

Abstract

The Hsp90 molecular chaperone is essential for protein homeostasis and in the maturation of proteins involved with cell-cycle control. The low ATPase activity of Hsp90 is critical to drive its functional cycle, which is dependent on the Hsp90 cochaperones. The Activator of Hsp90 ATPase-1 (Aha1) is a protein formed by two domains, N- and C-terminal, that stimulates the Hsp90 ATPase activity by several folds. Although the relevance of Aha1 for Hsp90 functions has been proved, as well as its involvement in the desensitization to inhibitors of the Hsp90, the knowledge on its overall structure and behavior in solution is limited. In this work we present the functional and structural characterization of Leishmania braziliensis Aha1 (LbAha1). This protozoan is the causative agent of cutaneous and mucocutaneous leishmaniasis, a neglected disease. The recombinant LbAha1 behaves as an elongated monomer and is organized into two folded domains interconnected by a flexible linker. Functional experiments showed that LbAha1 interacts with L. braziliensis Hsp90 (LbHsp90) with micromolar dissociation constant in a stoichiometry of 2 LbAha1 to 1 LbHsp90 dimer and stimulates 10-fold the LbHsp90 ATPase activity showing positive cooperativity. Furthermore, the LbHsp90:: LbAha1 complex is directed by enthalphy and opposed by entropy, probably due to the spatial freedom restrictions imposed by the proteins' interactions. Small-angle X-ray scattering data allowed the reconstruction of low resolution models and rigid body simulations of LbAha1, indicating its mode of action on LbHsp90. Western blot experiments allowed Aha1 identification (as well as Hsp90) in three Leishmania species at two temperatures, suggesting that Aha1 is a cognate protein. All these data shed light on the LbAha1 mechanism of action, showing that it has structural dimensions and flexibility that allow interacting with both N-terminal and middle domains of the LbHsp90. (AU)

• FAPESP's process: 11/23110-0 - Using isothermal titration calorimetry for the determination of thermodynamic properties of protein-ligand and protein-protein interactions
• Grantee: Julio Cesar Borges
• Support Opportunities: Regular Research Grants
• FAPESP's process: 08/09025-8 - Study of the molecular chaperone Hsp90 and its co-chaperone p23 from Plasmodium falciparum and Leishmania braziliensis
• Grantee: Kelly Pereira da Silva
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 12/50161-8 - Study of the structure and function of the Hsp90 chaperone with emphasis on its role in cellular homeostasis
• Grantee: Carlos Henrique Inacio Ramos
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 12/01953-9 - Proteins under fibrillation process: a structural and spectroscopic study of the influence of denaturating agents
• Grantee: Leandro Ramos Souza Barbosa
• Support Opportunities: Regular Research Grants
• FAPESP's process: 10/19242-6 - Study of the functional cycle of the Hsp90 molecular chaperone of protozoa and of the action of the co-chaperone Activator of the Hsp90 ATPase Activity - AHA1
• Grantee: Thiago Vargas Seraphim
• Support Opportunities: Scholarships in Brazil - Doctorate