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Example sentences for: zn
How can you use “zn” in a sentence? Here are some example sentences to help you improve your vocabulary:
Metal analyses of the S224A and S224D mutants showed that both mutants bind nearly two Zn(II) ions (Table 2), like wild-type L1 [ 36 ] ; however, the S224K mutant binds only 1.0 Zn(II) per protein.
It also has high affinity for binding to single-stranded DNA on its own when separated from the three tetracysteine motifs [ 36 ] . Based on the structural and DNA-binding properties of the E. coli topoisomerase I 14 kDa domain, one can conclude that it is possible for a subdomain in topoisomerase I to lose the Zn(II) binding cysteines during evolution and still maintains the Zn-ribbon structure and single-strand DNA binding properties [ 7 ] .
These estimates are in excellent agreement with the crystallographically determined secondary structure of ~40% α-helix and 30% β-structure [ 37 ] . Metal analyses on multiple preparations of wild-type L1 demonstrated that the enzyme binds 1.9 ± 0.2 Zn(II) ions per monomer (Table 2), in agreement with previous results [ 36 ] .
Steady-state kinetic studies were conducted with both mutants in buffer containing 100 μM ZnCl 2 to ensure that both Zn(II) binding sites were saturated in these studies.
There are over 300 distinct β-lactamases known, and these enzymes have been grouped by a number of classification schemes [ 8 9 10 11 12 13 14 15 ] . For example, Bush has developed a scheme, based on the enzymes' molecular properties, that has four distinct β-lactamase groups [ 10 15 ] . One of the more alarming groups are the Bush group 3 enzymes, which are Zn(II) dependent enzymes that hydrolyze nearly all known β-lactam containing antibiotics and for which there are no or very few known clinical inhibitors [ 9 14 16 17 18 19 ] . The metallo-β-lactamases have been further divided by Bush into subgroups based on amino acid sequence identity: the Ba enzymes share a >23% sequence identity, require 2 Zn(II) ions for full activity, prefer penicillins and cephalosporins as substrates, and are represented by metallo-β-lactamase CcrA from Bacteroides fragilis, the Bb enzymes share a 11% sequence identity with the Ba enzymes, require only 1 Zn(II) ion for full activity, prefer carbapenems as substrates, and are represented by the metallo-β-lactamase imiS from Aeromonas sobria, and the Bc enzymes have only 9 conserved residues with the other metallo-β-lactamases, require 2 Zn(II) ions for activity, contain a different metal binding motif than the other metallo-β-lactamases, prefer penicillins as substrates, and are represented by the metallo-β-lactamase L1 from Stenotrophomonas maltophilia [ 9 ] . A similar grouping scheme (B1, B2, and B3) based on structural properties of the metallo-β-lactamases has recently been offered [ 41 ] . The diversity of the group 3 β-lactamases is best exemplified by the enzymes' vastly differing efficacies towards non-clinical inhibitors; these differences predict that one inhibitor may not inhibit all metallo-β-lactamases [ 18 20 21 22 23 24 25 26 27 28 29 ] . To combat this problem, we are characterizing a metallo-β-lactamase from each of the subgroups in an effort to identify a common structural or mechanistic aspect of the enzymes that can be targeted for the generation of an inhibitor.
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