Oxidative damage of proline residues by nitrate radicals (NO3˙): a kinetic and product study

2020 ◽  
Vol 18 (35) ◽  
pp. 6949-6957
Author(s):  
Joses G. Nathanael ◽  
Jonathan M. White ◽  
Annika Richter ◽  
Madison R. Nuske ◽  
Uta Wille
Keyword(s):  
Amino Acid ◽  
Oxidative Damage ◽  
Kinetic Studies ◽  
Single Amino Acid ◽  
Peptide Bonds ◽  
Nitrate Radicals ◽  
Product Study

Kinetic studies in acetonitrile revealed that proline residues in peptides are considerably protected against radical-induced oxidative damage by the neighbouring peptide bonds, compared with the single amino acid.

scholarly journals Carbapenem-Resistant Strain of Klebsiella oxytoca Harboring Carbapenem-Hydrolyzingβ -Lactamase KPC-2

2003 ◽  
Vol 47 (12) ◽  
pp. 3881-3889 ◽  
Author(s):  
Hesna Yigit ◽  
Anne Marie Queenan ◽  
J. Kamile Rasheed ◽  
James W. Biddle ◽  
Antonio Domenech-Sanchez ◽  
...  
Keyword(s):  
Amino Acid ◽  
Clavulanic Acid ◽  
Outer Membrane Proteins ◽  
Klebsiella Oxytoca ◽  
Carbapenem Resistance ◽  
Kinetic Studies ◽  
Conjugative Plasmid ◽  
Single Amino Acid ◽  
Amino Acid Difference ◽  
Extended Spectrum

ABSTRACT We investigated a Klebsiella oxytoca isolate demonstrating resistance to imipenem, meropenem, extended-spectrum cephalosporins, and aztreonam. The MICs of both imipenem and meropenem were 32μ g/ml. The β-lactamase activity against imipenem and meropenem was inhibited in the presence of clavulanic acid. Isoelectric focusing studies demonstrated five β-lactamases with pIs of 8.2 (SHV-46), 6.7 (KPC-2), 6.5 (unknown), 6.4 (probable OXY-2), and 5.4 (TEM-1). The presence of the bla SHV and bla TEM genes was confirmed by specific PCR assays and DNA sequence analysis. Transformation and conjugation studies with Escherichia coli showed that the β-lactamase with a pI of 6.7, Klebsiella pneumoniae carbapenemase-2 (KPC-2), was encoded on an approximately 70-kb conjugative plasmid that also carried SHV-46, TEM-1, and the β-lactamase with a pI of 6.5. The bla KPC-2 determinant was cloned in E. coli and conferred resistance to imipenem, meropenem, extended-spectrum cephalosporins, and aztreonam. The amino acid sequence of KPC-2 showed a single amino acid difference, S174G, when compared with KPC-1, another carbapenem-hydrolyzing β-lactamase from K. pneumoniae 1534. Hydrolysis studies showed that purified KPC-2 hydrolyzed not only carbapenems but also penicillins, cephalosporins, and aztreonam. KPC-2 had the highest affinity for meropenem. The kinetic studies revealed that KPC-2 was inhibited by clavulanic acid and tazobactam. An examination of the outer membrane proteins of the parent K. oxytoca strain demonstrated that it expressed detectable levels of OmpK36 (the homolog of OmpC) and a higher-molecular-weight OmpK35 (the homolog of OmpF). Thus, carbapenem resistance in K. oxytoca 3127 is due to production of the Bush group 2f, class A, carbapenem-hydrolyzing β-lactamase KPC-2. This β-lactamase is likely located on a transposon that is part of a conjugative plasmid and thus has a very high potential for dissemination.

Single Amino Acid Based Self-Assemblies of Cysteine and Methionine

2018 ◽  
Author(s):  
Nidhi Gour ◽  
Bharti Koshti ◽  
Chandra Kanth P. ◽  
Dhruvi Shah ◽  
Vivek Shinh Kshatriya ◽  
...  
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Self Assembly ◽  
Aromatic Amino Acids ◽  
Neutral Condition ◽  
Single Amino Acid ◽  
Binding Assays ◽  
Human Neuroblastoma ◽  
Cytotoxicity Assays ◽  
First Time

We report for the very first time self-assembly of Cysteine and Methionine to discrenible strucutres under neutral condition. To get insights into the structure formation, thioflavin T and Congo red binding assays were done which revealed that aggregates may not have amyloid like characteristics. The nature of interactions which lead to such self-assemblies was purported by coincubating assemblies in urea and mercaptoethanol. Further interaction of aggregates with short amyloidogenic dipeptide diphenylalanine (FF) was assessed. While cysteine aggregates completely disrupted FF fibres, methionine albeit triggered fibrillation. The cytotoxicity assays of cysteine and methionine structures were performed on Human Neuroblastoma IMR-32 cells which suggested that aggregates are not cytotoxic in nature and thus, may not have amyloid like etiology. The results presented in the manuscript are striking, since to the best of our knowledge,this is the first report which demonstrates that even non-aromatic amino acids (cysteine and methionine) can undergo spontaneous self-assembly to form ordered aggregates.

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