The role of Zn2+ in Shal voltage-gated potassium channel formation.
Voltage-gated potassium channels are formed by the tetramerization of their alpha subunits, in a process that is controlled by their conserved N-terminal T1 domains. The crystal structures of Shaker and Shaw T1 domains reveal interesting differences in structures that are contained within a highly conserved BTB/POZ domain fold. The most surprising difference is that the Shaw T1 domain contains an intersubunit Zn2+ ion that is lacking in the Shaker T1 domain. The Zn2+ coordination motif is conserved in other non-Shaker channels making this the most distinctive difference between these channels and Shaker. In this study we show that Zn2+ is an important co-factor for the tetramerization of isolated Shaw and Shal T1 domains. Addition of Zn2+ increases the amount of tetramer formed, whereas chelation of Zn2+ with phenanthroline blocks tetramerization and causes assembled tetramers to disassemble. Within an intact cell, full-length Shal subunits containing Zn2+ site mutations also fail to form functional channels, with the majority of the protein found to remain monomeric by size exclusion chromatography. Therefore, zinc-mediated tetramerization also is a physiologically important event for full-length functional channel formation.
Strang
Candace
C
Neuroscience Division, Baylor College of Medicine, Houston, Texas 77030, USA.
Kunjilwar
Kumud
K
DeRubeis
David
D
Peterson
David
D
Pfaffinger
Paul J
PJ
D000818:Animals; D001048:Aplysia; D001665:Binding Sites; D016466:CHO Cells; D006224:Cricetinae; D003461:Crystallography; D008564:Membrane Potentials / Q000187:drug effects; D016296:Mutagenesis; D018408:Patch-Clamp Techniques; D010618:Phenanthrolines / Q000494:pharmacology; D015221:Potassium Channels / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D024642:Potassium Channels, Voltage-Gated; D017434:Protein Structure, Tertiary; D051381:Rats; D051637:Shaker Superfamily of Potassium Channels; D051672:Shal Potassium Channels; D051670:Shaw Potassium Channels; D013329:Structure-Activity Relationship; D015032:Zinc / Q000737:chemistry*
C497020:Kcnd2 protein, rat; D010618:Phenanthrolines; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D051637:Shaker Superfamily of Potassium Channels; D051672:Shal Potassium Channels; D051670:Shaw Potassium Channels; D015032:Zinc