Molecular characterization of glutaredoxin 5 from Penaeus vannamei and its potential roles in redox regulation and antibacterial defense

Glutaredoxin 5 (Grx5) is a member of the monothiol Grx family characterized by the conserved CGFS active-site motif and its involvement in iron–sulfur (Fe–S) cluster metabolism and cellular redox regulation. Although Grx5 proteins have been extensively studied in several model organisms, their biological roles in crustaceans remain poorly understood. In the present study, a Grx5 homolog from the white shrimp Penaeus vannamei (PvGrx5) was identified and characterized to investigate its molecular features and potential physiological functions. The PvGrx5 cDNA encodes a protein containing the conserved CGFS motif typical of monothiol Grxs. Multiple sequence alignment and phylogenetic analysis demonstrated that PvGrx5 clusters with other arthropod Grx5 homologs. This result indicates strong evolutionary conservation within this lineage. Structural modeling further revealed that PvGrx5 adopts a characteristic thioredoxin-like fold composed of a central β-sheet surrounded by α-helices, supporting its classification as a canonical monothiol Grx potentially involved in Fe–S cluster metabolism. Expression analysis showed that PvGrx5 transcripts were detected in all examined tissues, with relatively higher expression observed in gills and hemocytes. Furthermore, PvGrx5 expression was significantly upregulated following stimulation with pathogen-associated molecular patterns (PAMPs), including lipopolysaccharide (LPS), peptidoglycan (PGN), and polyinosinic:polycytidylic acid [poly(I:C)], suggesting that this gene responds to immune-related stress signals. Recombinant PvGrx5 (rPvGrx5) was successfully expressed in Escherichia coli and exhibited growth inhibitory effects against the shrimp pathogens Vibrio harveyi and Lactococcus garvieae, with a more pronounced effect observed for L. garvieae. Collectively, these findings provide the first molecular characterization of PvGrx5 in P. vannamei and suggest that this monothiol Grx may participate in physiological processes linking Fe–S cluster metabolism, cellular redox regulation, and immune responses in shrimp. This study expands current knowledge of Grx-mediated redox systems in crustaceans and provides a basis for further investigations into the roles of PvGrx5 in oxidative stress regulation and host defense.