Questions: 25 Most stable protein structure (6)

The answer is "domain."

Explanation:

1. The question is asking for a six-letter word that represents the most stable protein structure.
2. In the context of protein structures, a "domain" is a distinct functional and structural unit of a protein. Domains are often stable and can fold independently of the rest of the protein chain.
3. The word "domain" fits the requirement of being six letters long and is relevant to the context of protein stability.

Therefore, the most stable protein structure, as a six-letter word, is "domain."