4LS9: Structure Of Mycobacterial Nrna Homolog Reveals Multifunctional Nuclease Activities

DHH superfamily includes RecJ, nanoRNases (NrnA), cyclic nucleotide phosphodiesterases and pyrophosphatases. In this study, we have carried out in vitro and in vivo investigations on the bifunctional NrnA-homolog from Mycobacterium smegmatis, MSMEG_2630. The crystal structure of MSMEG_2630 was determined to 2.2-A resolution and reveals a dimer consisting of two identical subunits with each subunit folding into an N-terminal DHH domain and a C-terminal DHHA1 domain. The overall structure and fold of the individual domains is similar to other members of DHH superfamily. However, MSMEG_2630 exhibits a distinct quaternary structure in contrast to other DHH phosphodiesterases. This novel mode of subunit packing and variations in the linker region that enlarge the domain interface are responsible for alternate recognitions of substrates in the bifunctional nanoRNases. MSMEG_2630 exhibits bifunctional 3'-5' exonuclease [on both deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) substrates] as well as CysQ-like phosphatase activity (on pAp) in vitro with a preference for nanoRNA substrates over single-stranded DNA of equivalent lengths. A transposon disruption of MSMEG_2630 in M. smegmatis causes growth impairment in the presence of various DNA-damaging agents. Further phylogenetic analysis and genome organization reveals clustering of bacterial nanoRNases into two distinct subfamilies with possible role in transcriptional and translational events during stress.
PDB ID: 4LS9Download
MMDB ID: 121487
PDB Deposition Date: 2013/7/22
Updated in MMDB: 2014/07
Experimental Method:
x-ray diffraction
Resolution: 2.2  Å
Source Organism:
Similar Structures:
Biological Unit for 4LS9: dimeric; determined by author and by software (PISA)
Molecular Components in 4LS9
Label Count Molecule
Proteins (2 molecules)
DHH Family Protein
Molecule annotation
Chemicals (3 molecules)
* Click molecule labels to explore molecular sequence information.

Citing MMDB