Preliminary X‐ray diffraction and ligand‐binding analyses of the N‐terminal domain of hypothetical protein Rv1421 from Mycobacterium tuberculosis H37Rv.

Mycobacterium tuberculosis can reside and persist in deep tissues; latent tuberculosis can evade immune detection and has a unique mechanism to convert it into active disease through reactivation. M. tuberculosis Rv1421 (MtRv1421) is a hypothetical protein that has been proposed to be involved in nucleotide binding‐related metabolism in cell‐growth and cell‐division processes. However, due to a lack of structural information, the detailed function of MtRv1421 remains unclear. In this study, a truncated N‐terminal domain (NTD) of MtRv1421, which contains a Walker A/B‐like motif, was purified and crystallized using PEG 400 as a precipitant. The crystal of MtRv1421‐NTD diffracted to a resolution of 1.7 Å and was considered to belong to either the C‐centered monoclinic space group C2 or the I‐centered orthorhombic space group I222, with unit‐cell parameters a = 124.01, b = 58.55, c = 84.87 Å, β = 133.12° or a = 58.53, b = 84.86, c = 90.52 Å, respectively. The asymmetric units of the C2 or I222 crystals contained two or one monomers, respectively. In terms of the binding ability of MtRv1421‐NTD to various ligands, uridine diphosphate (UDP) and UDP‐N‐acetylglucosamine significantly increased the melting temperature of MtRv1421‐NTD, which indicates structural stabilization through the binding of these ligands. Altogether, the results reveal that a UDP moiety may be required for the interaction of MtRv1421‐NTD as a nucleotide‐binding protein with its ligand. [ABSTRACT FROM AUTHOR]