Project description:Here, we report on the site-specific O-glycosylation analysis of human blood plasma glycoproteins. To this end pooled human blood plasma of healthy donors was digested non-specifically using Protein-ase K, followed by a precipitation step, as well as a glycopeptide enrichment and fractionation step via hydrophilic interaction liquid chromatography. Enriched glycopeptide fractions were subjected to mass spectrometric analysis using reversed-phase liquid chromatography coupled online to an ion trap mass spectrometer operated in positive-ion mode. Peptide identity and glycan composition were derived from low-energy collision-induced dissociation fragment spectra acquired in multistage mode. To pinpoint the O-glycosylation sites glyco�peptides were fragmented using electron transfer dissociation. Spectra were annotated by database searches as well as manually. Overall, 31 O-glycosylation sites and regions belonging to 22 proteins were identified. The majority of these proteins were acute-phase proteins. Strikingly, also 11 novel O-glycosylation sites and regions were identified. In total 23 O-glycosylation sites could be pinpointed. Interestingly, the use of Proteinase K proved to be particularly beneficial in this context. The identified O-glycan compositions most probably correspond to mono- and disialylated core-1 mucin-type O-glycans (T-antigen).
Project description:CD209L is a membrane glycoprotein with known glycan-binding properties and it also contains 2 N-glycosylation sequons at sites N92 and N361. Treatment with PNGase F in the presence of H218O, which removes N-linked glycans and isotopically labels the formerly-glycosylated site, confirmed that both unmodified and formerly-glycosylated versions of the peptide spanning the N92 N-glycosylated sequon were present. This suggests that a portion of CD209L protein is N-glycosylated at site N92. nUPLC-MS/MS analyses of CD209L digests enabled detection of a glycopeptide consistent with high-mannose type N-linked glycosylation.
Project description:Human plasma fibronectin is an adhesive protein that plays a crucial role in wound healing. Many studies had indicated that glycans may mediate the expression and functions of fibronectin, yet a comprehensive understanding of its glycosylation is still missing. Here, we performed a comprehensive N- and O-glycosylation mapping of human plasma fibronectin, and quantified the occurrence of each glycoform in a site-specific manner. Intact N-glycopeptides were enriched by zwitterionic hydrophilic interaction chromatography, and N-glycosites sites were localized by the 18O-labeling method. O-glycopeptide enrichment and O-glycosite identification were achieved by an enzyme-assisted site-specific extraction method. An RP–LC–MS/MS system functionalized with Collision-Induced Dissociation and stepped normalized collision energy (sNCE)-HCD tandem mass was applied to analyze the glycoforms of fibronectin. A total of 6 N-glycosites and 53 O-glycosites were identified, which were occupied by 3842 N-glycoforms and 16 O-glycoforms, respectively. Furthermore, 81.4% of N-glycans were either fucosylated, sialylated, or with both modifications77.31% of N-glycans were sialylated, while O-glycosylation was dominated by the sialyl-T antigen. These site-specific glycosylation patterns on human fibronectin can facilitate functional analyses of fibronectin and therapeutics development.
Project description:A central tenet in the design of vaccines is the display of native-like antigens in the elicitation of protective immunity. The abundance of N-linked glycans across the SARS-CoV-2 spike protein is a potential source of heterogeneity between the many different vaccine candidates under investigation. Here, we investigate the glycosylation of recombinant SARS-CoV-2 spike proteins from five different laboratories and compare them against infectious virus S protein. We find patterns which are conserved across all samples and this can be associated with site-specific stalling of glycan maturation which act as a highly sensitive reporter of protein structure. Molecular dynamics (MD) simulations of a fully glycosylated spike support s a model of steric restrictions that shape enzymatic processing of the glycans. These results suggest that recombinant spike-based SARS-CoV-2 immunogen glycosylation reproducibly recapitulates signatures of viral glycosylation.
https://doi.org/10.1101/2021.03.08.433764
This folder contains the RAW MS files used in the glycopeptide analysis for recombinant SARS proteins from a range of different labs outlined in Figure 1 and 2 and additionally the analysis performed on monomeric RBD
Project description:Recombinant proteins are of great interest in glycobiology and proteomics, known especially for their reproducibility and accessibility. However, variation in glycosylation among recombinant glycoproteins is not well understood and may depend on numerous conditions in the biomanufacturing process. In order to confidently assess variation in glycosylation measurements, it is vital to both optimize the measurement of, and determine the degree of variation between, distributions of glycosylation on specific sites of glycoproteins. This is especially important for glycoproteins that are known to have rapid sequence changes, such as with different influenza strains. In this study, eight strains of recombinant influenza hemagglutinin and neuraminidase produced from HEK293 cell line were obtained from four vendors and digestion was conducted using a series of complex multi-enzymatic methods designed to isolate glycopeptide sequons. Site-specific glycosylation profiles of intact glycopeptides were produced using mass spectrometric evaluation on an orbitrap system and compared using spectral similarity scores. Variation in glycan abundances and distribution was most pronounced between different strains of virus (similarity score = 383 out of 1000), whereas replicates resulted in low variation (similarity score = 957 out of 1000). Glycan variation was also measured based on differences between vendors, lots, batches, protease digestion, and intra-protein site. The most abundant glycans in all of these influenza glycoproteins were monofucosylated and complex, as reported by other laboratories. However, it was found that different vendors can produce very different glycan distributions for the same glycosylation site. Notably, it is demonstrated that glycan distributions are similar for conserved regions of influenza glycoproteins. Overall, these methods present a potential use in developing reproducible measurements of glycosylated biologics for quality control or making more informed decisions in biomanufacturing.