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Figure 3
Overall structure of streptavidin C1. (a) Overall tetrameric structure of streptavidin C1. The C-terminal region named C-Lid and the flexible loop region (Loop3–4) are represented as orange and cyan cartoon models, respectively. The monomers are labeled Mol A, Mol B, Mol C and Mol D and are colored gray, marine, yellow and purple, respectively. (c) Surface representation of the streptavidin C1 tetramer. Mol A and Mol B (as well as Mol C and Mol D) closely interact to form a stable dimer, and two dimers assemble into a tetramer. The color code is the same as in (a). (c) Enlarged view of C-Lid and ECP, which interact with various hydrophobic residues such as Leu58, Val80, Trp140, Phe156 (Mol A) and Trp152 (located on Loop7–8 of the neighboring Mol C). (d) Overall tetrameric structure of streptavidin C1 complexed with biotin. Biotin is represented as a ball-and-stick model in green. (e) Surface representation of tetrameric streptavidin C1 complexed with biotin. (f) Enlarged view of the biotin-binding site of streptavidin C1.

IUCrJ
Volume 8| Part 2| March 2021| Pages 168-177
ISSN: 2052-2525
https://doi.org/10.1107/S2052252520015675