Conformational diversity defines substrate specificity of thymidylate/uridylate kinase from Candida albicans

2021 ◽  
Author(s):  
Kaustubh Sinha ◽  
Gordon S. Rule
Keyword(s):  
Candida Albicans ◽  
Substrate Specificity ◽  
Conformational Diversity ◽  
Uridylate Kinase

High-affinity myo-inositol transport in Candida albicans: substrate specificity and pharmacology

Microbiology ◽  
2003 ◽  
Vol 149 (12) ◽  
pp. 3371-3381 ◽  
Author(s):  
Jean Huaqian Jin ◽  
Andreas Seyfang
Keyword(s):  
Candida Albicans ◽  
Substrate Specificity ◽  
Pathogenic Fungus ◽  
Critical Role ◽  
Signal Transduction Pathway ◽  
Structural Similarity ◽  
Yeast Cells ◽  
Hydroxyl Groups ◽  
High Affinity ◽  
Sodium Dependent

Inositol is considered a growth factor in yeast cells and it plays an important role in Candida as an essential precursor for phospholipomannan, a glycophosphatidylinositol (GPI)-anchored glycolipid on the cell surface of Candida which is involved in the pathogenicity of this opportunistic fungus and which binds to and stimulates human macrophages. In addition, inositol plays an essential role in the phosphatidylinositol signal transduction pathway, which controls many cell cycle events. Here, high-affinity myo-inositol uptake in Candida albicans has been characterized, with an apparent K m value of 240±15 μM, which appears to be active and energy-dependent as revealed by inhibition with azide and protonophores (FCCP, dinitrophenol). Candida myo-inositol transport was sodium-independent but proton-coupled with an apparent K m value of 11·0±1·1 nM for H+, equal pH 7·96±0·05, suggesting that the C. albicans myo-inositol–H+ transporter is fully activated at physiological pH. C. albicans inositol transport was not affected by cytochalasin B, phloretin or phlorizin, an inhibitor of mammalian sodium-dependent inositol transport. Furthermore, myo-inositol transport showed high substrate specificity for inositol and was not significantly affected by hexose or pentose sugars as competitors, despite their structural similarity. Transport kinetics in the presence of eight different inositol isomers as competitors revealed that proton bonds between the C-2, C-3 and C-4 hydroxyl groups of myo-inositol and the transporter protein play a critical role for substrate recognition and binding. It is concluded that C. albicans myo-inositol–H+ transport differs kinetically and pharmacologically from the human sodium-dependent myo-inositol transport system and constitutes an attractive target for delivery of cytotoxic inositol analogues in this pathogenic fungus.

scholarly journals Inhibitor Resistant Mutants Give Important Insights into Candida albicans ABC Transporter Cdr1 Substrate Specificity and Help Elucidate Efflux Pump Inhibition

2021 ◽  
Author(s):  
Masakazu Niimi ◽  
Kyoko Niimi ◽  
Koichi Tanabe ◽  
Richard D. Cannon ◽  
Erwin Lamping
Keyword(s):  
Candida Albicans ◽  
Substrate Specificity ◽  
Abc Transporters ◽  
Fungal Pathogens ◽  
Efflux Pump ◽  
Binding Pocket ◽  
Kinetic Properties ◽  
Multidrug Efflux Pump ◽  
Resistant Mutants ◽  
Substrate Inhibitor

Overexpression of ATP-binding cassette (ABC) transporters is a major cause of drug resistance in fungal pathogens. Milbemycins, enniatin B, beauvericin and FK506 are promising leads for broad-spectrum fungal multidrug efflux pump inhibitors. The characterization of naturally generated inhibitor resistant mutants is a powerful tool to elucidate structure-activity relationships in ABC transporters. We isolated twenty Saccharomyces cerevisiae mutants overexpressing Candida albicans ABC pump Cdr1 variants resistant to fluconazole efflux inhibition by milbemycin α25 (eight mutants), enniatin B (eight) or beauvericin (four). The twenty mutations were in just nine residues at the centres of transmembrane segment 1 (TMS1) (six mutations), TMS4 (four), TMS5 (four), TMS8 (one) and TMS11 (two) and in A713P (three), a previously reported FK506-resistant ‘hotspot 1’ mutation in extracellular loop 3. Six Cdr1-G521S/C/V/R (TMS1) variants were resistant to all four inhibitors, four Cdr1-M639I (TMS4) isolates were resistant to milbemycin α25 and enniatin B, and two Cdr1-V668I/D (TMS5) variants were resistant to enniatin B and beauvericin. The eight milbemycin α25 resistant mutants were altered in four amino acids: G521R, M639I, A713P and T1355N. These four Cdr1 variants responded differently to various types of inhibitors, and each exhibited altered substrate specificity and kinetic properties. The data infer an entry gate function for Cdr1-G521 and a role for Cdr1-A713 in the constitutively high Cdr1 ATPase activity. Cdr1-M639I and -T1355N (TMS11) possibly cause inhibitor-resistance by altering TMS-contacts near the substrate/inhibitor-binding pocket. Models for the interactions of substrates and different types of inhibitors with Cdr1 at various stages of the transport cycle are presented.

Substrate specificity and inducibility of TACE (tumour necrosis factor α-converting enzyme) revisited: the Ala-Val preference, and induced intrinsic activity

2003 ◽  
Vol 70 ◽  
pp. 39-52 ◽  
Author(s):  
Roy A. Black ◽  
John R. Doedens ◽  
Rajeev Mahimkar ◽  
Richard Johnson ◽  
Lin Guo ◽  
...  
Keyword(s):  
Substrate Specificity ◽  
Recent Work ◽  
Tumour Necrosis Factor ◽  
Tumour Necrosis ◽  
Transforming Growth Factor ◽  
Intrinsic Activity ◽  
Converting Enzyme ◽  
Tumour Necrosis Factor Α ◽  
Factor Α ◽  
Necrosis Factor

Tumour necrosis factor α (TNFα)-converting enzyme (TACE/ADAM-17, where ADAM stands for a disintegrin and metalloproteinase) releases from the cell surface the extracellular domains of TNF and several other proteins. Previous studies have found that, while purified TACE preferentially cleaves peptides representing the processing sites in TNF and transforming growth factor α, the cellular enzyme nonetheless also sheds proteins with divergent cleavage sites very efficiently. More recent work, identifying the cleavage site in the p75 TNF receptor, quantifying the susceptibility of additional peptides to cleavage by TACE and identifying additional protein substrates, underlines the complexity of TACE-substrate interactions. In addition to substrate specificity, the mechanism underlying the increased rate of shedding caused by agents that activate cells remains poorly understood. Recent work in this area, utilizing a peptide substrate as a probe for cellular TACE activity, indicates that the intrinsic activity of the enzyme is somehow increased.

Enhanced IgE response to Candida albicans in postoperative invasive candidiasis

1996 ◽  
Vol 26 (4) ◽  
pp. 452-460 ◽  
Author(s):  
J. SAVOLAINEN ◽  
A. RANTALA ◽  
M. NERMES ◽  
L. LEHTONEN ◽  
M. VIANDER
Keyword(s):  
Candida Albicans ◽  
Invasive Candidiasis ◽  
Ige Response

Existence of Candida albicans and microorganisms in denture stomatitis patients

1997 ◽  
Vol 24 (10) ◽  
pp. 788-790 ◽  
Author(s):  
Y. KULAK ◽  
A. ARIKAN ◽  
E. KAZAZOGLU
Keyword(s):  
Candida Albicans ◽  
Denture Stomatitis
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