THE ROLE OF HEME IN PLANT CHANNEL SKOR AND GORK VOLTAGE GATING

Open Access
Author:
Mittal, Rea
Area of Honors:
Biology
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
  • Timothy Jegla, Thesis Supervisor
  • Michael Axtell, Honors Advisor
Keywords:
  • Electrophysiology
  • stomata
  • GORK
  • SKOR
  • voltage clamping
  • CNBD
  • heme
Abstract:
Heme, an iron containing compound with a surrounding porphyrin ring, is important in biological processes. Heme can bind to a protein to have a large effect on its structure and activity. The biological role of heme extends to ion channel proteins, where the specific molecular mechanisms and sites by which heme affects the opening probability of an ion channel are unknown. GORK channels, or Guard cell outward rectifying K+ channels, are cyclic nucleotide binding domains that will be used to mechanistically understand this process. Guard cell regulation is important to understand because it greatly affects water use efficiency, photosynthesis, and stress tolerances. The mechanism by which heme can modulate Arabidopsis thaliana plant guard cell ion channels which are responsible for opening and closing stomata was investigated via voltage clamped electrophysiological recordings in Xenopus Laevis oocytes. The process by which redox factors provided by oxidizing environmental agents affect channel gating in relation to heme will also be similarly investigated. Additionally, the mechanism via which heme directly affects voltage gating will be investigated through voltage fluorometry. Voltage fluorometry allows us to directly measure voltage sensor movements independent of the channel opening by fluorescently tagging the voltage sensors and examining their movements during recordings with voltage changes as changes in fluorescence.