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Espinosa LA, Ramos Y, Andújar I, Torres EO, Cabrera G, Martín A, Roche D, Chinea G, Becquet M, González I, Canaán-Haden C, Nelson E, Rojas G, Pérez-Massón B, Pérez-Martínez D, Boggiano T, Palacio J, Lozada Chang SL, Hernández L, de la Luz Hernández KR, Markku S, Vitikainen M, Valdés-Balbín Y, Santana-Medero D, Rivera DG, Vérez-Bencomo V, Emalfarb M, Tchelet R, Guillén G, Limonta M, Pimentel E, Ayala M, Besada V, González LJ. In-solution buffer-free digestion allows full-sequence coverage and complete characterization of post-translational modifications of the receptor-binding domain of SARS-CoV-2 in a single ESI-MS spectrum. Anal Bioanal Chem 2021; 413:7559-7585. [PMID: 34739558 PMCID: PMC8569510 DOI: 10.1007/s00216-021-03721-w] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Revised: 09/16/2021] [Accepted: 10/05/2021] [Indexed: 11/04/2022]
Abstract
Subunit vaccines based on the receptor-binding domain (RBD) of the spike protein of SARS-CoV-2 provide one of the most promising strategies to fight the COVID-19 pandemic. The detailed characterization of the protein primary structure by mass spectrometry (MS) is mandatory, as described in ICHQ6B guidelines. In this work, several recombinant RBD proteins produced in five expression systems were characterized using a non-conventional protocol known as in-solution buffer-free digestion (BFD). In a single ESI-MS spectrum, BFD allowed very high sequence coverage (≥ 99%) and the detection of highly hydrophilic regions, including very short and hydrophilic peptides (2-8 amino acids), and the His6-tagged C-terminal peptide carrying several post-translational modifications at Cys538 such as cysteinylation, homocysteinylation, glutathionylation, truncated glutathionylation, and cyanylation, among others. The analysis using the conventional digestion protocol allowed lower sequence coverage (80-90%) and did not detect peptides carrying most of the above-mentioned PTMs. The two C-terminal peptides of a dimer [RBD(319-541)-(His)6]2 linked by an intermolecular disulfide bond (Cys538-Cys538) with twelve histidine residues were only detected by BFD. This protocol allows the detection of the four disulfide bonds present in the native RBD, low-abundance scrambling variants, free cysteine residues, O-glycoforms, and incomplete processing of the N-terminal end, if present. Artifacts generated by the in-solution BFD protocol were also characterized. BFD can be easily implemented; it has been applied to the characterization of the active pharmaceutical ingredient of two RBD-based vaccines, and we foresee that it can be also helpful to the characterization of mutated RBDs.
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Affiliation(s)
- Luis Ariel Espinosa
- Center for Genetic Engineering and Biotechnology, Ave 31, e/ 158 y 190, Cubanacán, Playa, Havana, Cuba
| | - Yassel Ramos
- Center for Genetic Engineering and Biotechnology, Ave 31, e/ 158 y 190, Cubanacán, Playa, Havana, Cuba
| | - Ivan Andújar
- Center for Genetic Engineering and Biotechnology, Ave 31, e/ 158 y 190, Cubanacán, Playa, Havana, Cuba
| | - Enso Onill Torres
- Center for Genetic Engineering and Biotechnology, Ave 31, e/ 158 y 190, Cubanacán, Playa, Havana, Cuba
| | - Gleysin Cabrera
- Center for Genetic Engineering and Biotechnology, Ave 31, e/ 158 y 190, Cubanacán, Playa, Havana, Cuba
| | - Alejandro Martín
- Center for Genetic Engineering and Biotechnology, Ave 31, e/ 158 y 190, Cubanacán, Playa, Havana, Cuba
| | - Diamilé Roche
- Center for Genetic Engineering and Biotechnology, Ave 31, e/ 158 y 190, Cubanacán, Playa, Havana, Cuba
| | - Glay Chinea
- Center for Genetic Engineering and Biotechnology, Ave 31, e/ 158 y 190, Cubanacán, Playa, Havana, Cuba
| | - Mónica Becquet
- Center for Genetic Engineering and Biotechnology, Ave 31, e/ 158 y 190, Cubanacán, Playa, Havana, Cuba
| | - Isabel González
- Center for Genetic Engineering and Biotechnology, Ave 31, e/ 158 y 190, Cubanacán, Playa, Havana, Cuba
| | - Camila Canaán-Haden
- Center for Genetic Engineering and Biotechnology, Ave 31, e/ 158 y 190, Cubanacán, Playa, Havana, Cuba
| | - Elías Nelson
- Center for Genetic Engineering and Biotechnology, Ave 31, e/ 158 y 190, Cubanacán, Playa, Havana, Cuba
| | - Gertrudis Rojas
- Center of Molecular Immunology, 216 St., P.O. Box 16040, Havana, Cuba
| | | | | | - Tamy Boggiano
- Center of Molecular Immunology, 216 St., P.O. Box 16040, Havana, Cuba
| | - Julio Palacio
- Center of Molecular Immunology, 216 St., P.O. Box 16040, Havana, Cuba
| | | | - Lourdes Hernández
- Center of Molecular Immunology, 216 St., P.O. Box 16040, Havana, Cuba
| | | | - Saloheimo Markku
- VTT Technical Research Centre of Finland Ltd, P.O. Box 1000, 02044 VTT, Espoo, Finland
| | - Marika Vitikainen
- VTT Technical Research Centre of Finland Ltd, P.O. Box 1000, 02044 VTT, Espoo, Finland
| | | | | | - Daniel G Rivera
- Laboratory of Synthetic and Biomolecular Chemistry, Faculty of Chemistry, University of Havana, Zapata & G, 10400, Havana, Cuba
| | | | - Mark Emalfarb
- Dyadic International, Inc, 140 Intercoastal Pointe Drive, Suite #404, Jupiter, FL, 33477, USA
| | - Ronen Tchelet
- Dyadic International, Inc, 140 Intercoastal Pointe Drive, Suite #404, Jupiter, FL, 33477, USA
| | - Gerardo Guillén
- Center for Genetic Engineering and Biotechnology, Ave 31, e/ 158 y 190, Cubanacán, Playa, Havana, Cuba
| | - Miladys Limonta
- Center for Genetic Engineering and Biotechnology, Ave 31, e/ 158 y 190, Cubanacán, Playa, Havana, Cuba
| | - Eulogio Pimentel
- Center for Genetic Engineering and Biotechnology, Ave 31, e/ 158 y 190, Cubanacán, Playa, Havana, Cuba
| | - Marta Ayala
- Center for Genetic Engineering and Biotechnology, Ave 31, e/ 158 y 190, Cubanacán, Playa, Havana, Cuba
| | - Vladimir Besada
- Center for Genetic Engineering and Biotechnology, Ave 31, e/ 158 y 190, Cubanacán, Playa, Havana, Cuba
| | - Luis Javier González
- Center for Genetic Engineering and Biotechnology, Ave 31, e/ 158 y 190, Cubanacán, Playa, Havana, Cuba.
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