Figure 6.

Two possible tetramers in the crystal of 1auv. In the upper figure, the left complex surrounded by the green line is the biological tetramer according to the primary citation of this entry, and the right one surrounded by the yellow line is another possibility. Both tetramers are tightly packed with each other in the crystal. The lower figures show the biological contacts in these two tetramers by the arrows having the same color as the line surrounding the corresponding tetramer. The green arrow with “2 (BIO)” represents the biological contact which has the second largest area in the left tetramer. The yellow arrow with “2 (CRY)” corresponds to the crystal-packing contact which is the second largest contact in the right tetramer and is also the crystal-packing contact formed between the left tetramer and the neighboring tetramer including the right half of the right tetramer on the left side. The arrows with “1” represent the contacts with the largest area in both tetramers; these two contacts can be similar.