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Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
Sequences of PG-1 and PG-4. The same amino acids are represented by the same color. PG-4 substitutes a phenylalanine for a valine at position 14, and their sequences are different in the β-turn.