Study of the structural and functional interactions of homoserine dehydrogenases from the fungi Cryptococcus neoformans and Paracoccidioides brasiliensis

• Grant number: 24/20590-1
• Support Opportunities: Regular Research Grants
• Start date: October 01, 2025
• End date: September 30, 2028
• Field of knowledge: Biological Sciences - Biochemistry - Chemistry of Macromolecules
• Principal Investigator: Fernanda Canduri
• Grantee: Fernanda Canduri
• Host Institution: Instituto de Química de São Carlos (IQSC). Universidade de São Paulo (USP). São Carlos , SP, Brazil
• City of the host institution: São Carlos
• Associated researchers: FLAVIO AUGUSTO VICENTE SEIXAS ; José Henrique Pereira ; Marcio Vinicius Bertacine Dias
• Associated scholarship(s): 25/22680-0 - Functional and structural study of mutant forms of homoserine dehydrogenase from Paracoccidioides brasiliensis (PbHSD), BP.MS

Abstract

Invasive fungal infections are a global public health problem. It is estimated that 11.5 million serious infections and recurrent superficial mycoses are caused by fungi, with 1.5 million deaths resulting from these infections annually worldwide. In Brazil, it is estimated that 4 million people contract fungal infections each year. Cryptococcosis and paracoccidioidomycosis are systemic mycoses whose etiological agents are Cryptococcus spp. and Paracoccidioides spp., respectively, with C. neoformans and P. brasiliensis being the most virulent. Both are contracted through contact with contaminated soil and are opportunistic infections. They can develop in various organs of the body and evolve into severe forms of disease that can lead to death. There are no specific medications for the treatment of these diseases, which can last up to 24 months, leading to treatment abandonment and the emergence of resistant strains. In this sense, homoserine dehydrogenases (HSDs) are promising targets in the fight against fungi, since these enzymes are part of the aspartate metabolic pathway, which is not present in human metabolism. The objective of this work is to study homoserine dehydrogenases from both fungi mentioned above, obtained by heterologous expression in the bacterial system (E. coli), fused to the SUMO fusion protein, and purified by liquid affinity chromatography. Specific alterations will be made in the catalytic site of the HSDs, which, together with the non-mutant forms, will be targets of structural and functional analyses, using low and high resolution techniques: circular dichroism, differential scanning fluorescence, differential scanning calorimetry, UV-Vis spectrophotometry and isothermal titration calorimetry, as well as crystallization tests, all in the presence or absence of ligands. The comparative study of the different mutants may provide crucial information about the protein-ligand interaction mode of the HSDs of the fungi C. neoformans and P. brasiliensis. (AU)