{'fraction_non_alphanumeric': 0.022673964034401875, 'fraction_numerical': 0.033620015637216574, 'mean_word_length': 5.009389671361502, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Molecular basis for dimer formation of TRβ variant D355R

Protein quality and stability are critical during protein purification for X‐ray crystallography. A target protein that is easy to manipulate and crystallize becomes a valuable product useful for high‐throughput crystallography for drug design and discovery. In this work, a single surface mutation, D355R, was shown to be crucial for converting the modestly stable monomeric ligand binding domain of the human thyroid hormone receptor (TR LBD) into a stable dimer. The structure of D335R TR LBD mutant was solved using X‐ray crystallography and refined to 2.2 Å resolution with Rfree/R values of 24.5/21.7. The crystal asymmetric unit reveals the TR dimer with two molecules of the hormone‐bound LBD related by twofold symmetry. The ionic interface between the two LBDs comprises residues within loop H10‐H11 and loop H6‐H7 as well as the C‐terminal halves of helices 8 of both protomers. Direct intermolecular contacts formed between the introduced residue Arg 355 of one TR molecule and Glu 324 of the second molecule become a part of the extended dimerization interface of 1330 Å2 characteristic for a strong complex assembly that is additionally strengthened by buffer solutes. Proteins 2009. © 2008 Wiley‐Liss, Inc.