Lopez-Rodriguez A , Holmgren M .

	Figure 1. Temporal course of PNGase F action on Shaker KV channel. Western blot showing the reduction of molecular weight after enzymatic digestion of the sugar moiety with PNGase F (1 mg/ml; n = 5).
	Figure 2. Effects of deglycosylation on the ionic currents carried by Shaker KV channels. (A and B) Ionic currents from an oocyte expressing Shaker KV channels before (A) and after (B) 5-min exposure to PNGase F. Ionic currents were recorded by using the two-microelectrode voltage-clamp technique. These currents were elicited by 50-ms voltage steps from a holding potential of −80 to +40 mV, every 10 mV. (C) Time rise from 10% to 90% current activation. (D) Relative conductance plots before (black) and after (red) PNGase F treatment. Error bars in C and D represent mean ± SEM, (n = 5). DeGly, deglycosylation.
	Figure 3. Activation from glycosylation-deficient mutant Shaker KV channels. Rise time from 10% to 90% current activation from N259D–N263D mutant Shaker KV channels (n = 3) and N259Q–N263Q mutant Shaker KV channels (n = 3) and, for comparative purposes, those after PNGase F treatment. These data derived from ionic currents recorded using the two-microelectrode voltage clamp technique. Error bars represent mean ± SEM. DeGly, deglycosylation.
	Figure 4. PNGase F treatment of glycosylation-deficient mutant Shaker KV channels. (A) Normalized and superimposed ionic current traces from WT Shaker KV channels before and after PNGase F treatment, shown for comparative purposes. (B and C) Normalized and superimposed ionic current recordings before and after PNGase F treatment of oocytes expressing glycosylation-deficient N259D–N263D Shaker KV channels (B, n = 3) and N259Q–N263Q Shaker KV channels (C, n = 3). These experiments were performed with the same batch of PNGase F enzyme. These ionic currents were elicited in response to a voltage step to +60 mV from a holding potential of −80 mV and were recorded by using the cut-open oocyte voltage-clamp technique. DeGly, deglycosylation.
	Figure 5. Effect of deglycosylation on gating currents from the nonconducting (W434F) mutant Shaker KV channel. (A) Gating currents from an oocyte expressing nonconductive Shaker KV channels before (black) and after (red) 5-min exposure to PNGase F. Gating currents were elicited in response to voltage steps from −100 mV to the voltage shown on the traces by using the cut-open oocyte voltage clamp. (B) Voltage dependence of the gating charge before and after PNGase F treatment from the experiment shown in A. Solid lines represent Boltzmann fits. The best parameter values for the total amount of charge (Qtot) and the midpoint voltage (V1/2) were 2.42 nC and −55.4 mV before treatment and 1.94 nC and −48.7 mV after PNGase F treatment, respectively. The reduction in Qtot was observed in all experiments. It progresses with a slow time constant (∼60 min) to ∼30% of the initial value of Qtot. The reason for this response is unknown presently, but it appears to be specific for the nonconducting W434F mutant channel. (C) Normalized voltage dependence of the steady-state charge distribution. The plot shows the charge distribution before (black symbols) and after (red symbols) PNGase F treatment from seven experiments. In all experiments, the V1/2 shifted to the right in the voltage axes. (D) Box plot of the changes in V1/2 from the seven experiments.
	Figure 6. Effect of deglycosylation on ionic currents from the ILT mutant Shaker KV channel. (A) Normalized ionic current traces elicited from a holding potential of −100 mV to +100 mV (left) and +120 mV (right), before (black) and after (red) PNGase F treatment. (B) Normalized tail currents before (black) and after (red) PNGase F treatment upon return from the voltage step to +120 mV. Left: Zoomed-in traces depicted in A (+120 mV). Right: Traces from a different oocyte. Ionic currents from ILT channels were P/6 subtracted with subpulses of opposite polarity from the holding potential. These experiments were performed by using the cut-open oocyte voltage clamp. DeGly, deglycosylation.
	Figure 7. Effect of deglycosylation on the binding of Hanatoxin. (A and B) Current traces represent ionic currents in response to voltage steps to −50, −40, 0, and +40 mV from a holding potential of −80 mV. Tail currents shown were in response to voltage of −50 mV. In A, 200 nM HaTx was tested on unmodified channels (n = 5) and in B after deglycosylation by PNGase F (n = 4). (C) Relative probability of opening estimated from the tail currents. Data in the presence of HaTx were normalized with respect to the control (black and gray symbols) or immediately after PNGase F treatment (red and cyan symbols). These experiments were performed by using the two-microelectrode voltage-clamp technique. Error bars represent mean ± SEM. DeGly, deglycosylation.
	Figure 8. Effect of deglycosylation on the binding of pore blockers. (A and B) Current traces represent ionic currents in response to voltage steps to −50, −40, 0, and +40 mV from a holding potential of −80 mV. Tail currents shown were in response to voltage of −50 mV. A compares the inhibition by 100 nM AgTx before (top) and after (bottom) PNGase F treatment (n = 2). At +40 mV, AgTx blocked 48% of the ionic current before and 62% after treatment, respectively. At 0 mV, it inhibited 48% of the ionic current before and 63% treatment, respectively. B compares the inhibition by 0.1 mM 4AP before (top) and after (bottom) PNGase F treatment (n = 2). At +40 mV, 4AP blocked 55% of the ionic current before and 53% after treatment, respectively. At 0 mV, it inhibited 48% of the ionic current before and 50% after treatment, respectively. These experiments were performed by using the two-microelectrode voltage-clamp technique. DeGly, deglycosylation.

Aggarwal, Contribution of the S4 segment to gating charge in the Shaker K+ channel. 1996, Pubmed, Xenbase

Aggarwal, Contribution of the S4 segment to gating charge in the Shaker K+ channel. 1996, Pubmed , Xenbase
Apweiler, On the frequency of protein glycosylation, as deduced from analysis of the SWISS-PROT database. 1999, Pubmed
Bennett, Isoform-specific effects of sialic acid on voltage-dependent Na+ channel gating: functional sialic acids are localized to the S5-S6 loop of domain I. 2002, Pubmed
Bezanilla, The voltage sensor in voltage-dependent ion channels. 2000, Pubmed
Castillo, Changes in sodium channel function during postnatal brain development reflect increases in the level of channel sialidation. 1997, Pubmed
Covarrubias, Inhibitors of asparagine-linked oligosaccharide processing alter the kinetics of the nicotinic acetylcholine receptor. 1989, Pubmed
Deal, The brain Kv1.1 potassium channel: in vitro and in vivo studies on subunit assembly and posttranslational processing. 1994, Pubmed
Drain, Regulation of Shaker K+ channel inactivation gating by the cAMP-dependent protein kinase. 1994, Pubmed , Xenbase
Faillace, Cellular processing of cone photoreceptor cyclic GMP-gated ion channels: a role for the S4 structural motif. 2004, Pubmed
Freeman, Glycosylation influences gating and pH sensitivity of I(sK). 2000, Pubmed
Fujita, Glycosylation and cell surface expression of Kv1.2 potassium channel are regulated by determinants in the pore region. 2006, Pubmed
Garcia, Purification and characterization of three inhibitors of voltage-dependent K+ channels from Leiurus quinquestriatus var. hebraeus venom. 1994, Pubmed , Xenbase
Gross, Agitoxin footprinting the shaker potassium channel pore. 1996, Pubmed , Xenbase
Gurnett, Dual function of the voltage-dependent Ca2+ channel alpha 2 delta subunit in current stimulation and subunit interaction. 1996, Pubmed , Xenbase
Hall, Complex N-Glycans Influence the Spatial Arrangement of Voltage Gated Potassium Channels in Membranes of Neuronal-Derived Cells. 2015, Pubmed
Herrington, Blockers of the delayed-rectifier potassium current in pancreatic beta-cells enhance glucose-dependent insulin secretion. 2006, Pubmed
Holmgren, Regulation of Ion Channel and Transporter Function Through RNA Editing. 2015, Pubmed
Hoshi, Biophysical and molecular mechanisms of Shaker potassium channel inactivation. 1990, Pubmed , Xenbase
Ivanina, Phosphorylation by protein kinase A of RCK1 K+ channels expressed in Xenopus oocytes. 1994, Pubmed , Xenbase
Johnson, Gating of the shaker potassium channel is modulated differentially by N-glycosylation and sialic acids. 2008, Pubmed
Khanna, Glycosylation increases potassium channel stability and surface expression in mammalian cells. 2001, Pubmed , Xenbase
Kirsch, Segmental exchanges define 4-aminopyridine binding and the inner mouth of K+ pores. 1993, Pubmed
Kirsch, Gating-dependent mechanism of 4-aminopyridine block in two related potassium channels. 1993, Pubmed , Xenbase
Lainé, Atomic proximity between S4 segment and pore domain in Shaker potassium channels. 2003, Pubmed , Xenbase
Ledwell, Mutations in the S4 region isolate the final voltage-dependent cooperative step in potassium channel activation. 1999, Pubmed , Xenbase
Lee, Two separate interfaces between the voltage sensor and pore are required for the function of voltage-dependent K(+) channels. 2009, Pubmed , Xenbase
Lee, A membrane-access mechanism of ion channel inhibition by voltage sensor toxins from spider venom. 2004, Pubmed
Levin, Phosphorylation of a K+ channel alpha subunit modulates the inactivation conferred by a beta subunit. Involvement of cytoskeleton. 1996, Pubmed , Xenbase
Li-Smerin, Localization and molecular determinants of the Hanatoxin receptors on the voltage-sensing domains of a K(+) channel. 2000, Pubmed , Xenbase
Li-Smerin, Helical structure of the COOH terminus of S3 and its contribution to the gating modifier toxin receptor in voltage-gated ion channels. 2001, Pubmed
Long, Crystal structure of a mammalian voltage-dependent Shaker family K+ channel. 2005, Pubmed
Meighan, Cyclic nucleotide-gated channel subunit glycosylation regulates matrix metalloproteinase-dependent changes in channel gating. 2013, Pubmed , Xenbase
Milescu, Tarantula toxins interact with voltage sensors within lipid membranes. 2007, Pubmed , Xenbase
Milescu, Interactions between lipids and voltage sensor paddles detected with tarantula toxins. 2009, Pubmed
Milescu, Opening the shaker K+ channel with hanatoxin. 2013, Pubmed , Xenbase
Moremen, Vertebrate protein glycosylation: diversity, synthesis and function. 2012, Pubmed
Much, Role of subunit heteromerization and N-linked glycosylation in the formation of functional hyperpolarization-activated cyclic nucleotide-gated channels. 2003, Pubmed
Napp, Glycosylation of Eag1 (Kv10.1) potassium channels: intracellular trafficking and functional consequences. 2005, Pubmed , Xenbase
Pabon, Glycosylation of GIRK1 at Asn119 and ROMK1 at Asn117 has different consequences in potassium channel function. 2000, Pubmed
Pathak, The cooperative voltage sensor motion that gates a potassium channel. 2005, Pubmed , Xenbase
Perozo, Gating currents from a nonconducting mutant reveal open-closed conformations in Shaker K+ channels. 1993, Pubmed
Petrecca, N-linked glycosylation sites determine HERG channel surface membrane expression. 1999, Pubmed
Phillips, Position and motions of the S4 helix during opening of the Shaker potassium channel. 2010, Pubmed
Phillips, Voltage-sensor activation with a tarantula toxin as cargo. 2005, Pubmed
Recio-Pinto, Neuraminidase treatment modifies the function of electroplax sodium channels in planar lipid bilayers. 1990, Pubmed
Santacruz-Toloza, Glycosylation of shaker potassium channel protein in insect cell culture and in Xenopus oocytes. 1994, Pubmed , Xenbase
Schwalbe, Potassium channel structure and function as reported by a single glycosylation sequon. 1995, Pubmed
Seoh, Voltage-sensing residues in the S2 and S4 segments of the Shaker K+ channel. 1996, Pubmed , Xenbase
Shi, Differential asparagine-linked glycosylation of voltage-gated K+ channels in mammalian brain and in transfected cells. 1999, Pubmed
Smith-Maxwell, Role of the S4 in cooperativity of voltage-dependent potassium channel activation. 1998, Pubmed , Xenbase
Smith-Maxwell, Uncharged S4 residues and cooperativity in voltage-dependent potassium channel activation. 1998, Pubmed , Xenbase
Southan, The IUPHAR/BPS Guide to PHARMACOLOGY in 2016: towards curated quantitative interactions between 1300 protein targets and 6000 ligands. 2016, Pubmed
Sutachan, Effects of Kv1.1 channel glycosylation on C-type inactivation and simulated action potentials. 2005, Pubmed
Swartz, Mapping the receptor site for hanatoxin, a gating modifier of voltage-dependent K+ channels. 1997, Pubmed
Swartz, Tarantula toxins interacting with voltage sensors in potassium channels. 2007, Pubmed
Swartz, Hanatoxin modifies the gating of a voltage-dependent K+ channel through multiple binding sites. 1997, Pubmed , Xenbase
Taglialatela, Novel voltage clamp to record small, fast currents from ion channels expressed in Xenopus oocytes. 1992, Pubmed , Xenbase
Tarentino, Enzymatic deglycosylation of asparagine-linked glycans: purification, properties, and specificity of oligosaccharide-cleaving enzymes from Flavobacterium meningosepticum. 1994, Pubmed
Thornhill, Expression of Kv1.1 delayed rectifier potassium channels in Lec mutant Chinese hamster ovary cell lines reveals a role for sialidation in channel function. 1996, Pubmed
Ufret-Vincenty, Differential contribution of sialic acid to the function of repolarizing K(+) currents in ventricular myocytes. 2001, Pubmed
Ufret-Vincenty, Role of sodium channel deglycosylation in the genesis of cardiac arrhythmias in heart failure. 2001, Pubmed
Varki, Biological roles of oligosaccharides: all of the theories are correct. 1993, Pubmed
Watanabe, The degree of N-glycosylation affects the trafficking and cell surface expression levels of Kv1.4 potassium channels. 2015, Pubmed
Watanabe, Glycosylation affects rat Kv1.1 potassium channel gating by a combined surface potential and cooperative subunit interaction mechanism. 2003, Pubmed
Watanabe, The glycosylation state of Kv1.2 potassium channels affects trafficking, gating, and simulated action potentials. 2007, Pubmed
Watanabe, Glycosylation affects the protein stability and cell surface expression of Kv1.4 but Not Kv1.1 potassium channels. A pore region determinant dictates the effect of glycosylation on trafficking. 2004, Pubmed
Wirkner, Characterization of rat transient receptor potential vanilloid 1 receptors lacking the N-glycosylation site N604. 2005, Pubmed
Yifrach, Energetics of pore opening in a voltage-gated K(+) channel. 2002, Pubmed , Xenbase
Zhang, Glycosylation influences voltage-dependent gating of cardiac and skeletal muscle sodium channels. 1999, Pubmed
Zhu, Allowed N-glycosylation sites on the Kv1.2 potassium channel S1-S2 linker: implications for linker secondary structure and the glycosylation effect on channel function. 2003, Pubmed
Zhu, Determinants involved in Kv1 potassium channel folding in the endoplasmic reticulum, glycosylation in the Golgi, and cell surface expression. 2001, Pubmed