期刊
GENE
卷 555, 期 2, 页码 438-447出版社
ELSEVIER
DOI: 10.1016/j.gene.2014.11.013
关键词
Heterologous expression; In-vitro protein refolding; Molecular modeling and docking; Ni-NTA agarose affinity column chromatography; Rapid Amplification of cDNA Ends (RACE)
资金
- University Grant Commission (UGC), New Delhi (in the form of UGC-SRF)
- Department of Biotechnology (DBT), New Delhi under BIF
- Department of Higher Education, Government of U.P., Lucknow under the Centre of Excellence Grant
- Department of Science and Technology, New Delhi under the Promotion of University Research and Scientific Excellence (DST-PURSE) programme
Fruit ripening associated full length cDNA of a peroxidase from papaya was cloned and heterologously expressed. The expressed peroxidase was activated by in-vitro re-folding in the presence of hemin and calcium. The purified recombinant peroxidase exhibited broad substrate affinity in the order of o-dianisidine > pyrogallol > guaiacol and was found to be a homotetramer of 155 kDa with each subunit having a size of 38 kDa. The basis of the distinctive preferences for various substrates was investigated through in-silico molecular modeling approaches. Thus, when the modeled papaya peroxidase-heme complex was docked with these substrates, the in-silico binding efficiency was found to be in agreement with those of wet lab results with the involvement of Arg37, Phe40, His41, Pro137, Asn138, His139, His167, and Phe239 as the common interacting residues in all the cases. However, the binding of the different substrates were found to be associated with conformational changes in the peroxidase. Thus, in the case of o-dianisidine (the most efficient substrate), the protein was folded in the most compact fashion when compared to guaiacol (the least efficient substrate). Protein function annotation analyses revealed that the papaya peroxidase may have biological roles in oxidation-reduction processes, stresses, defense responses etc. In order to further validate its role in lignifications, the papaya peroxidase was compared with a lignin biosynthetic peroxidase from Leucaena leucocephala, a tree legume. Thus, based on 3D structure superimposition and docking, both peroxidases exhibited a great extent of similarity suggesting the papaya peroxidase having a role in lignification (defense response) too. The predicted functions of papaya peroxidase in defense response and lignification were further validated experimentally using gRT-PCR analyses and measurement of oxidation of coniferyl alcohol. (C) 2014 Elsevier B.V. All rights reserved.
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