Mechanisms of biotin-regulated gene expression in microbes

AbstractBiotin is an essential micronutrient that acts as a co-factor for biotin-dependent metabolic enzymes. In bacteria, the supply of biotin can be achieved by de novo synthesis or import from exogenous sources. Certain bacteria are able to obtain biotin through both mechanisms while others can only fulfill their biotin requirement through de novo synthesis. Inability to fulfill their cellular demand for biotin can have detrimental consequences on cell viability and virulence. Therefore understanding the transcriptional mechanisms that regulate biotin biosynthesis and transport will extend our knowledge about bacterial survival and metabolic adaptation during pathogenesis when the supply of biotin is limited. The most extensively characterized protein that regulates biotin synthesis and uptake is BirA. In certain bacteria, such as Escherichia coli and Staphylococcus aureus, BirA is a bi-functional protein that serves as a transcriptional repressor to regulate biotin biosynthesis genes, as well as acting as a ligase to catalyze the biotinylation of biotin-dependent enzymes. Recent studies have identified two other proteins that also regulate biotin synthesis and transport, namely BioQ and BioR. This review summarizes the different transcriptional repressors and their mechanism of action. Moreover, the ability to regulate the expression of target genes through the activity of a vitamin, such as biotin, may have biotechnological applications in synthetic biology

Tuberculosis control in Jiangsu province, China

Published: April 26, 2016Li Yan, Zhu Limei, Cheng Chen, Lu Wei, Booker G.W, Yu Hao, and Polyak S.W

Advanced resistance studies identify two discrete mechanisms in staphylococcus aureus to overcome antibacterial compounds that target biotin protein ligase

Biotin protein ligase (BPL) inhibitors are a novel class of antibacterial that target clinically important methicillin-resistant Staphylococcus aureus (S. aureus). In S. aureus, BPL is a bifunctional protein responsible for enzymatic biotinylation of two biotin-dependent enzymes, as well as serving as a transcriptional repressor that controls biotin synthesis and import. In this report, we investigate the mechanisms of action and resistance for a potent anti-BPL, an antibacterial compound, biotinyl-acylsulfamide adenosine (BASA). We show that BASA acts by both inhibiting the enzymatic activity of BPL in vitro, as well as functioning as a transcription co-repressor. A low spontaneous resistance rate was measured for the compound (<10-9) and whole-genome sequencing of strains evolved during serial passaging in the presence of BASA identified two discrete resistance mechanisms. In the first, deletion of the biotin-dependent enzyme pyruvate carboxylase is proposed to prioritize the utilization of bioavailable biotin for the essential enzyme acetyl-CoA carboxylase. In the second, a D200E missense mutation in BPL reduced DNA binding in vitro and transcriptional repression in vivo. We propose that this second resistance mechanism promotes bioavailability of biotin by derepressing its synthesis and import, such that free biotin may outcompete the inhibitor for binding BPL. This study provides new insights into the molecular mechanisms governing antibacterial activity and resistance of BPL inhibitors in S. aureus.Andrew J. Hayes, Jiulia Satiaputra, Louise M. Sternicki, Ashleigh S. Paparella, Zikai Feng, Kwang J. Lee ... et al

Identification and targeted management of a neurodegenerative disorder caused by biallelic mutations in SLC5A6

We describe a sibling pair displaying an early infantile-onset, progressive neurodegenerative phenotype, with symptoms of developmental delay and epileptic encephalopathy developing from, to, months of age. Using whole exome sequencing, compound heterozygous variants were identified in SLC, A, which encodes the sodium-dependent multivitamin transporter, SMVT, protein. SMVT is an important transporter of the B-group vitamins biotin, pantothenate, and lipoate. The protein is ubiquitously expressed and has major roles in vitamin uptake in the digestive system, as well as transport of these vitamins across the blood, brain barrier. Pathogenicity of the identified variants was demonstrated by impaired biotin uptake of mutant SMVT. Identification of this vitamin transporter as the genetic basis of this disorder guided targeted therapeutic intervention, resulting clinically in improvement of the patient, s neurocognitive and neuromotor function. This is the second report of biallelic mutations in SLC, A, leading to a neurodegenerative disorder due to impaired biotin, pantothenate and lipoate uptake. The genetic and phenotypic overlap of these cases confirms mutations in SLC, A, as the genetic cause of this disease phenotype. Recognition of the genetic disorder caused by SLC, A, mutations is essential for early diagnosis and to facilitate timely intervention by triple vitamin, biotin, pantothenate, and lipoate, replacement therapy.Steven W. Polyak ... Andreas W. Schreiber ... Christopher N. Hahn ... Dylan A. Mordaunt ... Drago Bratkovic, Grant W. Booker, Nicholas J. Smith, Hamish S. Scot

The role of biotin in bacterial physiology and virulence: A novel antibiotic target for Mycobacterium tuberculosis

Tuberculosis (TB) is a global pandemic that ranks alongside HIV-AIDS and malaria as the leading cause of death by infectious disease, with the highest incidence rates observed in Southeast Asian, African, and Western Pacific countries ( 1 ). In 1993 the WHO declared TB to be a global health emergency and set the Millennium Development Goal of reducing the prevalence and mortality rates to 50% of those observed in 1990 by the 2015 deadline ( 2 ). Although the rates of new TB cases and mortality have declined over the past decade and are within reach of the 2015 target, the number of TB patients and the prevalence of drug-resistant strains are rising ( 3 ). Multidrug-resistant TB (MDR-TB) must be addressed now as a public health crisis to achieve the ambitious Millennium Development Goal target of complete elimination of TB as a public health concern by 2050 ( 4 ).Wanisa Salaemae, Grant W. Booker, and Steven W. Polya

Mechanisms of biotin-regulated gene expression in microbes

Biotin is an essential micronutrient that acts as a co-factor for biotin-dependent metabolic enzymes. In bacteria, the supply of biotin can be achieved by de novo synthesis or import from exogenous sources. Certain bacteria are able to obtain biotin through both mechanisms while others can only fulfill their biotin requirement through de novo synthesis. Inability to fulfill their cellular demand for biotin can have detrimental consequences on cell viability and virulence. Therefore understanding the transcriptional mechanisms that regulate biotin biosynthesis and transport will extend our knowledge about bacterial survival and metabolic adaptation during pathogenesis when the supply of biotin is limited. The most extensively characterized protein that regulates biotin synthesis and uptake is BirA. In certain bacteria, such as Escherichia coli and Staphylococcus aureus, BirA is a bi-functional protein that serves as a transcriptional repressor to regulate biotin biosynthesis genes, as well as acting as a ligase to catalyze the biotinylation of biotin-dependent enzymes. Recent studies have identified two other proteins that also regulate biotin synthesis and transport, namely BioQ and BioR. This review summarizes the different transcriptional repressors and their mechanism of action. Moreover, the ability to regulate the expression of target genes through the activity of a vitamin, such as biotin, may have biotechnological applications in synthetic biology

Mycobacterium tuberculosis Dethiobiotin Synthetase Facilitates Nucleoside Triphosphate Promiscuity through Alternate Binding Modes

The penultimate step in the biosynthesis of biotin is the closure of the ureido heterocycle in a reaction requiring a nucleoside triphosphate (NTP). In Mycobacterium tuberculosis this reaction is catalyzed by dethiobiotin synthetase (MtDTBS). MtDTBS is unusual as it can employ multiple (NTPs), with a >100-fold preference for cytidine triphosphate (CTP). Here the molecular basis of NTP binding was investigated using a surface plasmon resonance-based ligand binding assay and X-ray crystallography. The biophysical and structural data revealed two discrete mechanisms by which MtDTBS binds NTPs: (i) A high affinity binding mode employed by CTP (KD 160 nM) that is characterized by a slow dissociation rate between enzyme and ligand (kd 5.3 × 10–2 s–1) and that is defined by an extended network of specific ligand–protein interactions involving both the cytidine and triphosphate moieties and (ii) a low affinity mode employed by the remaining NTPs (KD > 16.5 μM), that is characterized by weak interactions between protein and ligand. Previously intractable structures of MtDTBS in complex with ATP, GTP, UTP, and ITP were obtained to define the molecular basis of the low affinity ligand binding. Anchoring of the triphosphate moiety into the phosphate binding loop of MtDTBS allows the promiscuous utilization of multiple NTPs. Both high and low binding mechanisms showed conserved hydrogen bonding interactions involving the β-phosphate of NTPs and a high-affinity anion binding site within the phosphate binding loop. This study provides insights into enzymes that can likewise utilize multiple NTPs.Andrew P. Thompson, Wanisa Salaemae, Jordan L. Pederick, Andrew D. Abell, Grant W. Booker, John B. Bruning, Kate L. Wegener and Steven W. Polya