Biological gas channels for NH3 and CO2: evidence that Rh (Rhesus) proteins are CO2 channels
1Department of Plant and Microbial Biology, 111 Koshland Hall, University of California, Berkeley, Berkeley, CA 94720-3102, USA. kustu@nature.berkeley.edu
Abstract:
Physiological evidence from our laboratory indicates that Amt/Mep proteins are gas channels for NH3, the first biological gas channels to be described. This view has now been confirmed by structural evidence and is displacing the previous belief that Amt/Mep proteins were active transporters for the NH4+ ion. Still disputed is the physiological substrate for Rh proteins, the only known homologues of Amt/Mep proteins. Many think they are mammalian ammonium (NH4+ or NH3) transporters. Following Monod's famous dictum, "Anything found to be true of E. coli must also be true of elephants" [Perspect. Biol. Med. 47(1) (2004) 47], we explored the substrate for Rh proteins in the unicellular green alga Chlamydomonas reinhardtii. C. reinhardtii is one of the simplest organisms to have Rh proteins and it also has Amt proteins. Physiological studies in this microbe indicate that the substrate for Rh proteins is CO2 and confirm that the substrate for Amt proteins is NH3. Both are readily hydrated gases. Knowing that transport of CO2 is the ancestral function of Rh proteins supports the inference from hematological research that a newly evolving role of the human Rh30 proteins, RhCcEe and RhD, is to help maintain the flexible, flattened shape of the red cell.
More Related Videos
05:28Electrophysiology on Isolated Brainstem-spinal Cord Preparations from Newborn Rodents Allows Neural Respiratory Network Output Recording
Published on: November 19, 2015
10:34Exploring the Radical Nature of a Carbon Surface by Electron Paramagnetic Resonance and a Calibrated Gas Flow
Published on: April 24, 2014
Related Concept Videos
Channel Rhodopsins
Rhodopsins belong to the family of cell surface proteins called G-protein coupled receptors,...
Carbon Dioxide Transport in the Blood
Forms of CO2 Transport
1. Dissolved in plasma: A small percentage (7-10%) of CO2 is transported and dissolved directly in the plasma.
2. Carbaminohemoglobin: Just over 20% of CO2 is chemically bound to...
Chemical Factors Affecting Respiration Centers
CO2 has a potent influence on respiration and is strictly regulated. Under...
G-Protein Gated Ion Channels
Sensory organs,...
Respiratory Regulation of Acid-Base Balance
When carbon dioxide levels increase in the blood, more H+ and HCO3⁻ are produced, leading to a...
Gas Exchange and Transport
