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Structural characterization and comparative modeling of PD-Ls 1–3, type 1 ribosome-inactivating proteins from summer leaves of Phytolacca dioica L.

2008; Elsevier BV; Volume: 91; Issue: 3 Linguagem: Inglês

10.1016/j.biochi.2008.10.008

1638-6183

Antimo Di Maro, Angela Chambery, Vincenzo Carafa, Susan Costantini, Giovanni Colonna, Augusto Parente,

Plant Genetic and Mutation Studies

The amino acid sequence and glycan structure of PD-L1, PD-L2 and PD-L3, type 1 ribosome-inactivating proteins isolated from Phytolacca dioica L. leaves, were determined using a combined approach based on peptide mapping, Edman degradation and ESI-Q-TOF MS in precursor ion discovery mode. The comparative analysis of the 261 amino acid residue sequences showed that PD-L1 and PD-L2 have identical primary structure, as it is the case of PD-L3 and PD-L4. Furthermore, the primary structure of PD-Ls 1–2 and PD-Ls 3–4 have 81.6% identity (85.1% similarity). The ESI-Q-TOF MS analysis confirmed that PD-Ls 1–3 were glycosylated at different sites. In particular, PD-L1 contained three glycidic chains with the well known paucidomannosidic structure (Man)3 (GlcNAc)2 (Fuc)1 (Xyl)1 linked to Asn10, Asn43 and Asn255. PD-L2 was glycosylated at Asn10 and Asn43, and PD-L3 was glycosylated only at Asn10. PD-L4 was confirmed to be not glycosylated. Despite an overall high structural similarity, the comparative modeling of PD-L1, PD-L2, PD-L3 and PD-L4 has shown potential influences of the glycidic chains on their adenine polynucleotide glycosylase activity on different substrates.