Abstract
Glycosylation is one of the most abundant protein posttranslational modifications. Protein glycosylation plays important roles not only in eukaryotes but also in prokaryotes. To further understand the roles of protein glycosylation in prokaryotes, we developed a lectin binding assay to screen glycoproteins on an Escherichia coli proteome microarray containing 4,256 affinity-purified E.coli proteins. Twenty-three E.coli proteins that bound Wheat-Germ Agglutinin (WGA) were identified. PANTHER protein classification analysis showed that these glycoprotein candidates were highly enriched in metabolic process and catalytic activity classes. One sub-network centered on deoxyribonuclease I (sbcB) was identified. Bioinformatics analysis suggests that prokaryotic protein glycosylation may play roles in nucleotide and nucleic acid metabolism. Fifteen of the 23 glycoprotein candidates were validated by lectin (WGA) staining, thereby increasing the number of validated E. coli glycoproteins from 3 to 18. By cataloguing glycoproteins in E.coli, our study greatly extends our understanding of protein glycosylation in prokaryotes.
Highlights
Glycosylation is one of the most abundant protein posttranslational modifications (PTMs) [1]
Unbound lectin was removed by washing and the microarrays were scanned with a microarray scanner
Using a high-throughput E. coli proteome microarray and a glycan-specific lectin binding assay, we have globally screened for glycoproteins in E. coli
Summary
Glycosylation is one of the most abundant protein posttranslational modifications (PTMs) [1]. It is predicted that more than two-thirds of eukaryotic proteins are glycosylated [2] and that these modifications are essential for a multitude of biological processes such as fertilization [3], cancer metastasis [4] and host-pathogen interactions [5,6]. Protein glycosylation was first demonstrated in the late 1930s [7] and was long thought to occur only in eukaryotes [8]. Protein glycosylation occurs in bacteria, and more than 70 bacterial glycoproteins have been reported [10]. The vast majority of these glycoproteins are surface or secreted proteins and may play important roles in cellcell interactions, surface adhesion, or evasion of immune responses [10,11,12]
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