title: Selection of aptamers for signal transduction proteins by capillary electrophoresis.
abstract: High-affinity aptamers for important signal transduction proteins, i.e. Cdc42-GTP, p21-activated kinase1 (PAK1) and MRCK (myotonic dystrophy kinase-related Cdc42-binding kinase) alpha were successfully selected in the low micro- to nanomolar range using non-systematic evolution of ligands by exponential enrichment (SELEX) with at least three orders of magnitude enhancement from their respective bulk affinity of naïve DNA library. In the non-SELEX procedure, CE was used as a highly efficient affinity method to select aptamers for the desired molecular target through a process that involved repetitive steps of partitioning, known as non-equilibrium CE of equilibrium mixtures with no PCR amplification between successive steps. Various non-SELEX conditions including the type, concentration and pH of the run buffer were optimized. Other considerations such as salt composition of selection buffer, protein concentration and sample injection size were also studied for high stringency during selection. After identifying the best enriched aptamer pool, randomly selected clones from the aptamer pool were sequenced to obtain the individual DNA sequences. The dissociation constants (K(d)) of these sequences were in the low micromolar to nanomolar range, indicating high affinity to the respective proteins. The best binders were also subjected to sequence alignment to generate a phylogenetic tree. No significant consensus region based on approximately 50 sequences for each protein was observed, suggesting the high efficiency of non-SELEX for the selection of numerous unique sequences with high selectivity.
authors.affiliation: Department of Chemistry, National University of Singapore, Republic of Singapore, Singapore.
authors.forename: Junie
authors.initials: J
authors.lastname: Tok
authors.forename: Jesyin
authors.initials: J
authors.lastname: Lai
authors.forename: Thomas
authors.initials: T
authors.lastname: Leung
authors.forename: Sam Fong Yau
authors.initials: SF
authors.lastname: Li
mesh_terms: D052158:Aptamers, Peptide / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D002021:Buffers; D019075:Electrophoresis, Capillary / Q000379:methods*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D065636:Myotonin-Protein Kinase; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D020764:cdc42 GTP-Binding Protein / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D054462:p21-Activated Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D052158:Aptamers, Peptide; D002021:Buffers; D047908:Intracellular Signaling Peptides and Proteins; C105518:CDC42BPA protein, human; D065636:Myotonin-Protein Kinase; C515903:PAK1 protein, human; D017346:Protein Serine-Threonine Kinases; D054462:p21-Activated Kinases; D020764:cdc42 GTP-Binding Protein