Hydrolysis of diadenosine polyphosphates. Exploration of an additional role of Mycobacterium smegmatis MutT1

2017 ◽  
Vol 199 (3) ◽  
pp. 165-176 ◽  
Author(s):  
S.M. Arif ◽  
U. Varshney ◽  
M. Vijayan
2010 ◽  
Vol 192 (18) ◽  
pp. 4776-4785 ◽  
Author(s):  
Rabeb Dhouib ◽  
Françoise Laval ◽  
Frédéric Carrière ◽  
Mamadou Daffé ◽  
Stéphane Canaan

ABSTRACT MSMEG_0220 from Mycobacterium smegmatis, the ortholog of the Rv0183 gene from M. tuberculosis, recently identified and characterized as encoding a monoacylglycerol lipase, was cloned and expressed in Escherichia coli. The recombinant protein (rMSMEG_0220), which exhibits 68% amino acid sequence identity with Rv0183, showed the same substrate specificity and similar patterns of pH-dependent activity and stability as the M. tuberculosis enzyme. rMSMEG_0220 was found to hydrolyze long-chain monoacylglycerol with a specific activity of 143 ± 6 U mg−1. Like Rv0183 in M. tuberculosis, MSMEG_0220 was found to be located in the cell wall. To assess the in vivo role of the homologous proteins, an MSMEG_0220 disrupted mutant of M. smegmatis (MsΔ0220) was produced. An intriguing change in the colony morphology and in the cell interaction, which were partly restored in the complemented mutant containing either an active (ComMsΔ0220) or an inactive (ComMsΔ0220S111A) enzyme, was observed. Growth studies performed in media supplemented with monoolein showed that the ability of both MsΔ0220 and ComMsΔ0220S111A to grow in the presence of this lipid was impaired. Moreover, studies of the antimicrobial susceptibility of the MsΔ0220 strain showed that this mutant is more sensitive to rifampin and more resistant to isoniazid than the wild-type strain, pointing to a critical structural role of this enzyme in mycobacterial physiology, in addition to its function in the hydrolysis of exogenous lipids.


2017 ◽  
Vol 73 (4) ◽  
pp. 349-364 ◽  
Author(s):  
S. M. Arif ◽  
A. G. Patil ◽  
U. Varshney ◽  
M. Vijayan

Mycobacterium smegmatisMutT1, which is made up of a Nudix domain (domain 1) and a histidine phosphatase domain (domain 2), efficiently hydrolyses 8-oxo-GTP and 8-oxo-dGTP to the corresponding nucleoside diphosphates and phosphate in the presence of magnesium ions. Domain 1 alone hydrolyses nucleoside triphosphates less efficiently. Under high concentrations and over long periods, the full-length enzyme as well as domain 1 catalyses the hydrolysis of the nucleoside triphosphates to the respective nucleoside monophosphates and pyrophosphate. The role of domain 2 appears to be limited to speeding up the reaction. Crystal structures of the apoenzyme and those of ligand-bound enzyme prepared in the presence of 8-oxo-GTP or 8-oxo-dGTP and different concentrations of magnesium were determined. In all of the structures except one, the molecules arrange themselves in a head-to-tail fashion in which domain 1 is brought into contact with domain 2 (transdomain 2) of a neighbouring molecule. The binding site for NTP (site A) is almost exclusively made up of residues from domain 1, while those for NDP (site B) and NMP (site C) are at the interface between domain 1 andtransdomain 2 in an unusual instance of intermolecular interactions leading to binding sites. Protein–ligand interactions at site A lead to a proposal for the mechanism of hydrolysis of NTP to NDP and phosphate. A small modification in site A in the crystal which does not exhibit the head-to-tail arrangement appears to facilitate the production of NMP and pyrophosphate from NTP. The two arrangements could be in dynamic equilibrium in the cellular milieu.


Molecules ◽  
2021 ◽  
Vol 26 (10) ◽  
pp. 2852
Author(s):  
Paul A. Foster

Steroid sulphatase (STS), involved in the hydrolysis of steroid sulphates, plays an important role in the formation of both active oestrogens and androgens. Since these steroids significantly impact the proliferation of both oestrogen- and androgen-dependent cancers, many research groups over the past 30 years have designed and developed STS inhibitors. One of the main contributors to this field has been Prof. Barry Potter, previously at the University of Bath and now at the University of Oxford. Upon Prof. Potter’s imminent retirement, this review takes a look back at the work on STS inhibitors and their contribution to our understanding of sulphate biology and as potential therapeutic agents in hormone-dependent disease. A number of potent STS inhibitors have now been developed, one of which, Irosustat (STX64, 667Coumate, BN83495), remains the only one to have completed phase I/II clinical trials against numerous indications (breast, prostate, endometrial). These studies have provided new insights into the origins of androgens and oestrogens in women and men. In addition to the therapeutic role of STS inhibition in breast and prostate cancer, there is now good evidence to suggest they may also provide benefits in patients with colorectal and ovarian cancer, and in treating endometriosis. To explore the potential of STS inhibitors further, a number of second- and third-generation inhibitors have been developed, together with single molecules that possess aromatase–STS inhibitory properties. The further development of potent STS inhibitors will allow their potential therapeutic value to be explored in a variety of hormone-dependent cancers and possibly other non-oncological conditions.


Genetics ◽  
1991 ◽  
Vol 128 (1) ◽  
pp. 45-57 ◽  
Author(s):  
C T Kuan ◽  
S K Liu ◽  
I Tessman

Abstract Excision and transposition of the Tn5 element in Escherichia coli ordinarily appear to occur by recA-independent mechanisms. However, recA(Prtc) genes, which encode RecA proteins that are constitutively activated to the protease state, greatly enhanced excision and transposition; both events appeared to occur concomitantly and without destruction of the donor DNA. The recombinase function of the RecA protein was not required. Transposition was accompanied by partial, and occasionally full, restoration of the functional integrity of the gene vacated by the excised Tn5. The stimulation of transposition was inhibited by an uncleavable LexA protein and was strongly enhanced by an additional role of the RecA(Prtc) protein besides its mediation of LexA cleavage. To account for the enhanced transposition, we suggest that (i) there may be a LexA binding site within the promoter for the IS50 transposase, (ii) activated RecA may cleave the IS50 transposition inhibitor, and (iii) the transposase may be formed by RecA cleavage of a precursor molecule.


1983 ◽  
Vol 258 (22) ◽  
pp. 13673-13679 ◽  
Author(s):  
A Gómez-Puyou ◽  
G Ayala ◽  
U Muller ◽  
M Tuena de Gómez-Puyou

2016 ◽  
Vol 199 ◽  
pp. 49-58 ◽  
Author(s):  
Shaoni Sun ◽  
Shaolong Sun ◽  
Xuefei Cao ◽  
Runcang Sun

2015 ◽  
Vol 1 (7) ◽  
pp. e1500263 ◽  
Author(s):  
Akihiko Nakamura ◽  
Takuya Ishida ◽  
Katsuhiro Kusaka ◽  
Taro Yamada ◽  
Shinya Fushinobu ◽  
...  

Hydrolysis of carbohydrates is a major bioreaction in nature, catalyzed by glycoside hydrolases (GHs). We used neutron diffraction and high-resolution x-ray diffraction analyses to investigate the hydrogen bond network in inverting cellulase PcCel45A, which is an endoglucanase belonging to subfamily C of GH family 45, isolated from the basidiomycete Phanerochaete chrysosporium. Examination of the enzyme and enzyme-ligand structures indicates a key role of multiple tautomerizations of asparagine residues and peptide bonds, which are finally connected to the other catalytic residue via typical side-chain hydrogen bonds, in forming the “Newton’s cradle”–like proton relay pathway of the catalytic cycle. Amide–imidic acid tautomerization of asparagine has not been taken into account in recent molecular dynamics simulations of not only cellulases but also general enzyme catalysis, and it may be necessary to reconsider our interpretation of many enzymatic reactions.


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