A functional and stable truncated-phycoerythrin (T-PE) was found as a result of spontaneous in vitro truncation. Truncation was noticed to occur during storage of purified native-phycoerythrin (N-PE) isolated from Lyngbya sp. A09DM. SDS and native-PAGE analysis revealed the truncation of N-PE, containing α (19.0 kDa)--and β (21.5 kDa)--subunits to the only single peptide of ∼15.45 kDa (T-PE). The peptide mass fingerprinting (PMF) and MS/MS analysis indicated that T-PE is the part of α-subunit of N-PE. UV-visible absorption peak of N-PE was found to split into two peaks (540 and 565 nm) after truncation, suggesting the alterations in its folded state. The emission spectra of both N-PE and T-PE show the emission band centered at 581 nm (upon excitation at 559 nm) suggested the maintenance of fluorescence even after significant truncation. Urea-induced denaturation and Gibbs-free energy (ΔGD°) calculations suggested that the folding and structural stability of T-PE was almost similar to that of N-PE. Presented bunch of evidences revealed the truncation in N-PE without perturbing its folding, structural stability and functionality (fluorescence), and thereby suggested its applicability in fluorescence based biomedical techniques where smaller fluorescence molecules are more preferable.
Keywords: In vitro truncation; Phycoerythrin; Structural stability.
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