Banca de QUALIFICAÇÃO: MARIA LAURA DA SILVA

Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.
STUDENT : MARIA LAURA DA SILVA
DATE: 17/12/2025
TIME: 14:00
LOCAL: Departamento de Biologia
TITLE:

Evaluation of leishmanicidal activity of proteins extracted from photosynthetic microorganisms: an in silico analysis

KEY WORDS:

Arthrospira platensis, phycocyanin, ProtParam, intrinsic disorder, SLiMs, antiparasitc

PAGES: 70
BIG AREA: Ciências Agrárias
AREA: Medicina Veterinária
SUBÁREA: Medicina Veterinária Preventiva
SPECIALTY: Doenças Parasitárias de Animais
SUMMARY:

Leishmaniasis remains one of the major neglected tropical diseases, characterized by high morbidity and limitations of existing treatments, which include toxicity, high costs, and parasitic resistance. In this context, biomolecules produced by photosynthetic microorganisms, such as Arthrospira platensis phycocyanin, have shown promise. In silico analysis plays a crucial role, allowing rapid, low-cost, and highly precise structural and functional protein characterization, while reducing the need for animal experimentation in the early stages. This study investigated the physicochemical properties and antileishmanial potential of the α and β subunits of Arthrospira platensis phycocyanin, as well as their predisposition to intrinsic disorder.The subunit sequences were retrieved from UniProtKB using the keywords Arthrospira and Phycocyanin and analyzed using ProtParam to estimate parameters such as molecular weight, isoelectric point, amino acid composition, extinction coefficient, instability index, aliphatic index, and GRAVY. Intrinsic disorder prediction was performed on the RIDĀO platform, using the predictors PONDR VLXT, VSL2B, VL3, PONDR FIT, and IUPred Short and Long, with a threshold of 0.5 to classify disordered residues. In silico analysis revealed that the α subunit has a higher concentration of cationic residues, such as arginine and lysine, and a pI ranging from 5.75 to 9.90, while the β subunit has a predominance of anionic residues and a lower pI (4.23–6.15). The extinction coefficient was higher for the α subunit (between 21,890 and 22,015), associated with a higher concentration of tyrosine. Both subunits exhibited hydrophobic properties, with the β subunit showing a higher GRAVY value (94.4%), which may contribute to its interactions with the cationic membranes of Leishmania. The molecular weight of the α subunit ranged from 1.19 kDa to 17.63 kDa, while the β subunit ranged from 2.76 kDa to 18.09 kDa, with values consistent with those of documented antileishmanial peptides. The α subunit also showed greater stability, with 92.86% of its instability index (II) values below 40. The aliphatic index was 8.02% for the α subunit and 10.28% for the β subunit, with the latter showing a higher percentage of leucine, a crucial residue in antileishmanial peptides. The α subunit exhibited greater structural flexibility, with 30.06–55.93% of its proteins being intrinsically disordered, while the β subunit showed a more ordered structure. These results suggest that the α subunit, with greater structural flexibility and favorable physicochemical properties, is more promising for antileishmanial applications.

COMMITTEE MEMBERS:
Interna - ANA LUCIA FIGUEIREDO PORTO
Interna - RAQUEL PEDROSA BEZERRA
Externa à Instituição - PATRÍCIA PEREIRA DUZI CARVALHO - USP