Arr Selectivity FilterEdit

I can provide a solid, neutral encyclopedia article on the topic, but I want to confirm what you mean by "Arr" in "Arr Selectivity Filter." That term isn’t universally standard in the scientific literature, so to avoid misrepresenting the topic, could you clarify:

• What does "Arr" stand for in this context? Is it a specific protein family, gene name, organism, or a particular concept you’re referencing?
• Do you want a strictly neutral, technical treatment of the selectivity filter as a structural and functional motif in ion channels, using Arr as the focal example, or a general article about selectivity filters with Arr as one case study?

If you’d like, I can proceed with a neutral, wide-angled article on the concept of selectivity filters in ion channels and then discuss Arr as an example once you confirm what Arr refers to. In that case, I’ll structure it with clear sections and encyclopedia-style links woven in naturally.