title: A plate-based high-throughput activity assay for polysialyltransferase from Neisseria meningitidis.
abstract: Polysialyltransferases (PSTs) assemble polysialic acid (PSA) and have been implicated in many biological processes. For example, certain bacteria such as neuroinvasive Neisseria meningitidis decorate themselves in a PSA capsule to evade the innate immune system. Identifying inhibitors of PSTs therefore represents an attractive therapeutic goal and herein we describe a high-throughput, robust, and sensitive microtiter-plate-based activity assay for PST from N. meningitidis. A trisialyl lactoside (GT3) serving as the acceptor substrate was immobilized on a 384-well plate by click chemistry. Incubation with PST and CMP-sialic acid for 30min resulted in polysialylation. The immobilized PSA was then directly detected using a green fluorescent protein (GFP)-fused PSA-binding protein consisting of the catalytically inactive double mutant of an endosialidase (GFP-EndoNF DM). We report very good agreement between kinetic and inhibition parameters obtained with our on-plate assay versus our in-solution validation assay. In addition we prove our assay is robust and reliable with a Z' score of 0.79. All aspects of our assay are easily scalable owing to optimization trials that allowed immobilization of acceptor substrates prepared from crude reaction mixtures and the use of cell lysates. This assay methodology enables large-scale PST inhibitor screens and can be harnessed for directed evolution screens.
authors.affiliation: Department of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan.
authors.forename: Ching-Ching
authors.initials: CC
authors.lastname: Yu
authors.forename: Tara
authors.initials: T
authors.lastname: Hill
authors.forename: David H
authors.initials: DH
authors.lastname: Kwan
authors.forename: Hong-Ming
authors.initials: HM
authors.lastname: Chen
authors.forename: Chun-Cheng
authors.initials: CC
authors.lastname: Lin
authors.forename: Warren
authors.initials: W
authors.lastname: Wakarchuk
authors.forename: Stephen G
authors.initials: SG
authors.lastname: Withers
mesh_terms: D057075:Enzyme Assays / Q000379:methods*; D006027:Glycosides / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D057166:High-Throughput Screening Assays / Q000379:methods*; D015394:Molecular Structure; D009345:Neisseria meningitidis / Q000201:enzymology*; D012799:Sialyltransferases / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D006027:Glycosides; C008245:lactosides; D012799:Sialyltransferases
keywords: Click chemistry; Endosialidase; GFP; High-throughput screening; Polysialic acid; Polysialyltransferase