β‐ATPase of the Insect <scp><i>Panstrongylus megistus</i></scp>: Cloning, Bioinformatics Analysis, and Study of Its Interaction With Lipophorin

Lipophorin is the main lipoprotein of the insect's hemolymph. Although its role in lipid metabolism has been extensively analyzed, the mechanisms of lipid delivery to target tissues mediated by lipophorin are not completely understood. It has been reported that the β-chain of the ATP synthase complex (β-ATPase) acts as a nonendocytic receptor for lipophorin in the hematophagous insect Panstrongylus megistus, and this function is relevant for the transfer of lipids. The aim of this study was to gather new information regarding the β-ATPase, including its sequence and interaction with lipophorin. A β-ATPase cDNA encoding a 521-amino acid protein was cloned from P. megistus. β-ATPase is highly conserved, and molecular phylogenetic analyses grouped the deduced amino acid sequences according to their respective taxa. Structural modeling of β-ATPase revealed a conserved folding pattern and three-dimensional architecture that allows docking with a modeled lipophorin, suggesting potential interaction between the two proteins. Recombinant β-ATPase (rβ-ATPase) was expressed in Escherichia coli, and the rβ-ATPase was purified by affinity chromatography. rβ-ATPase was combined with lipophorin at various ratios, and the sedimentation properties of these mixtures were analyzed by analytical ultracentrifugation. The changes in sedimentation behavior of the protein mixture compared to that of the individual proteins are consistent with binding between rβ-ATPase and lipophorin. This finding, which confirms the interaction of β-ATPase and lipophorin, provides additional support for the role of β-ATPase in the uptake of lipids by tissues.