58 research outputs found
State-Dependent Accessibility of the P-S6 Linker of Pacemaker (HCN) Channels Supports a Dynamic Pore-to-Gate Coupling Model
The hyperpolarization-activated cyclic nucleotide-modulated channel gene family (HCN1-4) encodes the membrane depolarizing current that underlies pacemaking. Although the topology of HCN resembles Kv channels, much less is known about their structure-function correlation. Previously, we identified several pore residues in the S5-P linker and P-loop that are externally accessible and/or influence HCN gating, and proposed an evolutionarily conserved pore-to-gate mechanism. Here we sought dynamic evidence by assessing the functional consequences of Cys-scanning substitutions in the unexplored P-S6 linker (residues 352–359), the HCN1-R background (that is, resistant to sulfhydryl-reactive agents). None of A352C, Q353C, A354C, P355C, V356C, S357C, M358C, or S359C produced functional currents; the loss-of-function of Q353C, A354C, S357C, and M358C could be rescued by the reducing agent dithiothreitol. Q353C, A354C, and S357C, but not M358C and HCN1-R, were sensitive to Cd2+ blockade (IC50 = 3–12 μM vs. >1 mM). External application of the positively charged covalent sulfhydryl modifier MTSET irreversibly reduced I−140mV of Q353C and A354C to 27.9 ± 3.4% and 58.2 ± 13.1% of the control, respectively, and caused significant steady-state activation shifts (∆V1/2 = –21.1 ± 1.6 for Q353C and −10.0 ± 2.9 mV for A354C). Interestingly, MTSET reactivity was also state dependent. MTSET, however, affected neither S357C nor M358C, indicating site specificity. Collectively, we have identified novel P-S6 residues whose extracellular accessibility was sterically and state dependent and have provided the first functional evidence consistent with a dynamic HCN pore-to-gate model
George Skylitzes’ dedicatory verses for the Sacred Arsenal by Andronikos Kamateros and the Codex Marcianus Graecus 524
Analisi dei versi dedicatori scritti da Giorgio Scilitze per l'Arsenale Sacro di Andronico Camatero, in parallelo con l'analisi di alcuni epigrammi contenuti nel manoscritto Marciano Greco 52
EK e DIA: la processione dello Spirito Santo tra il XII ed il XIII secolo, spunti di riflessione
La processione dello Spirito Santo tra XI e XIII secol
Andronico Camatero e la zizzania: sulla politica ecclesiastica bizantina in età comnena
Politica ecclesiastica dell'imperatore Manuele Comnen
The Sacred Arsenal by Andronikos Kamateros, a forgotten treasure
L'Arsenale Sacro di Andronico Camatero, la fortuna dell'opera
Dibattiti teologici alla corte di Manuele Comneno
Sulla politica ecclesiastica di Manuele Comneno e gli autori che scrissero contro i Latini tra il IX e il XII secol
Dialogues and anthologies of the Sacred Arsenal by Andronikos Kamateros: sources, arrangements, purposes
Analisi delle finalità delle parti antologiche dell'Arsenal Sacro di Andronico Camater
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