A molecular receptor selective for zwitterionic alanine

2017 ◽  
Vol 15 (2) ◽  
pp. 477-485 ◽  
Author(s):  
Omayra H. Rubio ◽  
Rachid Taouil ◽  
Francisco M. Muñiz ◽  
Laura M. Monleón ◽  
Luis Simón ◽  
...  
Keyword(s):  
Amino Acid ◽  
Oxyanion Hole ◽  
Enantioselective Extraction

A new chiral chromane receptor has been synthesized with a right-sized oxyanion hole to fix zwitterionic alanine. This associate allows the enantioselective extraction of this amino acid from water to chloroform.

scholarly journals Chiral recognition with a benzofuran receptor that mimics an oxyanion hole

2015 ◽  
Vol 13 (2) ◽  
pp. 493-501 ◽  
Author(s):  
Ángel L. Fuentes de Arriba ◽  
Ángel Gómez Herrero ◽  
Omayra H. Rubio ◽  
Laura M. Monleón ◽  
Luis Simón Rubio ◽  
...  
Keyword(s):  
Amino Acid ◽  
Chiral Recognition ◽  
Chiral Resolution ◽  
Amino Acid Derivatives ◽  
Oxyanion Hole ◽  
Enantioselective Extraction

Chiral resolution of a novel tripodal oxyanion-hole receptor with application in amino acid derivatives enantioselective extraction.

scholarly journals Rhodococcus sp. Strain CR-53 LipR, the First Member of a New Bacterial Lipase Family (Family X) Displaying an Unusual Y-Type Oxyanion Hole, Similar to the Candida antarctica Lipase Clan

2012 ◽  
Vol 78 (6) ◽  
pp. 1724-1732 ◽  
Author(s):  
Arnau Bassegoda ◽  
F. I. Javier Pastor ◽  
Pilar Diaz
Keyword(s):  
Amino Acid ◽  
Amino Acid Sequence ◽  
Candida Antarctica ◽  
Burkholderia Cenocepacia ◽  
Sequence Motifs ◽  
Oxyanion Hole ◽  
Content Type ◽  
New Family ◽  
Consensus Amino Acid Sequence ◽  
Four Blocks

ABSTRACTBacterial lipases constitute the most important group of biocatalysts for synthetic organic chemistry. Accordingly, there is substantial interest in developing new valuable lipases. Considering the lack of information concerning the lipases of the genusRhodococcusand taking into account the interest raised by the enzymes produced by actinomycetes, a search for putative lipase-encoding genes fromRhodococcussp. strain CR-53 was performed. We isolated, cloned, purified, and characterized LipR, the first lipase described from the genusRhodococcus. LipR is a mesophilic enzyme showing preference for medium-chain-length acyl groups without showing interfacial activation. It displays good long-term stability and high tolerance for the presence of ions and chemical agents in the reaction mixture. Amino acid sequence analysis of LipR revealed that it displays four unique amino acid sequence motifs that clearly separate it from any other previously described family of bacterial lipases. Using bioinformatics tools, LipR could be related only to several uncharacterized putative lipases from different bacterial origins, all of which display the four blocks of consensus amino acid sequence motifs that contribute to define a new family of bacterial lipases, namely, family X. Therefore, LipR is the first characterized member of the new bacterial lipase family X. Further confirmation of this new family of lipases was performed after cloningBurkholderia cenocepaciaputative lipase, bearing the same conserved motifs and clustering in family X. Interestingly, all lipases grouping in the new bacterial lipase family X display a Y-type oxyanion hole, a motif conserved in theCandida antarcticalipase clan but never found among bacterial lipases. This observation contributes to confirm that LipR and its homologs belong to a new family of bacterial lipases.

scholarly journals Functional role of catalytic triad and oxyanion hole-forming residues on enzyme activity of Escherichia coli thioesterase I/protease I/phospholipase L1

2006 ◽  
Vol 397 (1) ◽  
pp. 69-76 ◽  
Author(s):  
Li-Chiun Lee ◽  
Ya-Lin Lee ◽  
Ruey-Jyh Leu ◽  
Jei-Fu Shaw
Keyword(s):  
Escherichia Coli ◽  
Enzyme Activity ◽  
Amino Acid ◽  
Water Molecule ◽  
Acyl Chain ◽  
Residual Activity ◽  
Catalytic Triad ◽  
The Other ◽  
Oxyanion Hole

Escherichia coli TAP (thioesterase I, EC 3.1.2.2) is a multifunctional enzyme with thioesterase, esterase, arylesterase, protease and lysophospholipase activities. Previous crystal structural analyses identified its essential amino acid residues as those that form a catalytic triad (Ser10-Asp154-His157) and those involved in forming an oxyanion hole (Ser10-Gly44-Asn73). To gain an insight into the biochemical roles of each residue, site-directed mutagenesis was employed to mutate these residues to alanine, and enzyme kinetic studies were conducted using esterase, thioesterase and amino-acid-derived substrates. Of the residues, His157 is the most important, as it plays a vital role in the catalytic triad, and may also play a role in stabilizing oxyanion conformation. Ser10 also plays a very important role, although the small residual activity of the S10A variant suggests that a water molecule may act as a poor substitute. The water molecule could possibly be endowed with the nucleophilic-attacking character by His157 hydrogen-bonding. Asp154 is not as essential compared with the other two residues in the triad. It is close to the entrance of the substrate tunnel, therefore it predominantly affects substrate accessibility. Gly44 plays a role in stabilizing the oxyanion intermediate and additionally in acyl-enzyme-intermediate transformation. N73A had the highest residual enzyme activity among all the mutants, which indicates that Asn73 is not as essential as the other mutated residues. The role of Asn73 is proposed to be involved in a loop75–80 switch-move motion, which is essential for the accommodation of substrates with longer acyl-chain lengths.

Structural and Functional Significance of Amino Acid Lysine192 (chymotrypsin numbering) in Factor XIa and Factor VIIa.

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 2030-2030
Author(s):  
Amy E Schmidt ◽  
Sayeh Agah ◽  
Mao-fu Sun ◽  
Kaillathe Padmanabhan ◽  
Duilio Cascio ◽  
...  
Keyword(s):  
Amino Acid ◽  
Serine Proteases ◽  
Peptide Bond ◽  
Side Chain ◽  
Hole Formation ◽  
Oxyanion Hole ◽  
Structural Role ◽  
Inhibitor Specificity ◽  
Modeling Studies ◽  
Substrate Inhibitor

Abstract In blood coagulation serine proteases, amino acid 192 (chymotrypsin numbering) influences substrate and inhibitor specificity, and also forms a peptide bond with Gly193, a critical part of the protease oxyanion hole. Residue 192 is either Glu or Gln in several serine proteases including thrombin, factor (F) Xa, FIXa, and activated protein C. However, it is Lys in factor FXIa and FVIIa. Both FXIa and FVIIa/tissue factor (TF) share FIX as their substrate. In addition, FVIIa/TF activates FX and is inhibited by TF pathway inhibitor (TFPI), whereas FXIa is inhibited by diisopropylfluorophosphate (DFP), p-aminobenzamidine (p-AB), antithrombin and amyloid-b precursor protein Kunitz domain (AbPP). We investigated the importance of Lys192 in FXIa and FVIIa for substrate/inhibitor specificity and oxyanion hole formation. Recombinant FXIa was prepared with Pro (FXIaK192P), Glu (FXIaK192E) or Gln (FXIaK192Q) substitutions for Lys192. Rate constants for inhibition by DFP were similar for wild type FXIa (FXIaWT), FXIaK192E and FXIaK192Q, but 80-fold slower for FXIaK192P. Only FXIaK192P differed in binding to pAB compared to FXIaWT. These data indicate that Pro192 causes distortion of the oxyanion hole and S1 binding site. All mutants bound the FXIa substrate FIX normally. However, catalysis of FIX was impaired 400, 35, and 110-fold for FXIaK192P, FXIaK192E, and FXIaK192Q, respectively, while k2 for inhibition by antithrombin was reduced 160, 15 and 16-fold. FXIaK192P bound to AbPP with 800-fold decreased affinity; while FXIaK192E and FXIaK192Q bound with 6-10-fold higher affinity. Modeling studies indicate that there is loss of the normal interaction between Lys192 and the substrate/inhibitor P3’ residue in interactions between FXIaK192E and FXIaK192Q and factor IX and antithrombin. The Ki for Glu and Gln mutant inhibition by AbPP is slightly better probably due to the ability of these two amino acids to make two H-bonds as compared to only one for Lys192. Lys192 makes H-bond with the carbonyl O of Gly12 in AbPP, whereas Glu and Gln at this position make H-bonds with the carbonyl O of Cys14 and Ala16 in AbPP. In FXIaK192P, the oxyanion hole is impaired due to a flip in the 192-193 peptide bond causing the amide N of Gly193 to point away from the oxyanion hole, resulting in a severe impairment of all catalytic functions. Thus a non-proline residue 192 is essential for proper oxyanion hole formation in serine proteases, and Lys192 in FXIa contributes significantly towards macromolecular substrate catalysis and inhibitor binding. In contrast to FXIaWT, the 192-193 peptide bond in FVIIaWT ± TF is already in a nonstandard conformation in which the amide N of Gly193 points away, and the carbonyl O of the Lys192 points into the oxyanion hole (Bajaj, et al., J. Biol. Chem.281, 24873-24888, 2006). The H-bond between the amide N of Gly193 and the carbonyl side chain of Gln143, a residue unique to FVIIa, maintains this nonstandard conformation in FVIIa. Notably, upon substrate binding the 192-193 bond flips 180° such that the oxyanion hole is fully formed. Now the H-bond is formed between the amide N of Gly193 and the carbonyl oxygen of the transition state intermediate. For this to occur, the H-bond between the amide N of Gly193 and the carbonyl side chain of Gln143 must first be broken. Previous studies have shown that changing Lys192 to Glu or Gln in FVIIa severely impairs its biologic activity. However, the structural basis for this impairment is not understood. We performed molecular modeling studies which reveal that the side chain of the Glu192 carboxyl group or of the Gln192 carbonyl group makes strong H-bond with the side chain NH2 group of Gln143; this is not possible for Lys192. Thus in Glu192 or Gln192 mutant of FVIIa, it is energetically difficult to break the H-bond between the amide N of Gly193 and the carbonyl side chain of Gln143 because the H-bond involving the side chain of Glu192 or Gln192 and the Gln143 must be simultaneously broken. This provides a structural rational for the impaired function of FVIIaK192E or FVIIaK192Q. To test this concept further, we prepared FVIIa in which Lys192 was replaced with alanine. All properties of this alanine mutant were normal substantiating the proposed structural role of Lys192 in FVIIa. This structural role is unique to FVIIa among all known serine proteases, as is the presence of residue Gln143 that contributes to this phenomenon.

The staining pattern of the tropomyosin sequence is displayed in a new paracrystal

1986 ◽  
Vol 44 ◽  
pp. 150-151
Author(s):  
M.K. Lamvik ◽  
L.L. Klatt
Keyword(s):  
Amino Acid ◽  
Amino Acid Sequence ◽  
Staining Pattern ◽  
Banding Patterns ◽  
Mass Thickness ◽  
New Form

Tropomyosin paracrystals have been used extensively as test specimens and magnification standards due to their clear periodic banding patterns. The paracrystal type discovered by Ohtsuki1 has been of particular interest as a test of unstained specimens because of alternating bands that differ by 50% in mass thickness. While producing specimens of this type, we came across a new paracrystal form. Since this new form displays aligned tropomyosin molecules without the overlaps that are characteristic of the Ohtsuki-type paracrystal, it presents a staining pattern that corresponds to the amino acid sequence of the molecule.

Electron probe x-ray microanalysis and electron microscopy of amino acid absorption and transport by the small intestine: inhibition by chemical poisons and correlation to the elemental composition of the epithelial cells

1986 ◽  
Vol 44 ◽  
pp. 134-135
Author(s):  
A. J. Tousimis
Keyword(s):  
Small Intestine ◽  
Amino Acid ◽  
Epithelial Cells ◽  
Elemental Composition ◽  
Isotope Labeling ◽  
Structural Components ◽  
X Ray ◽  
Human Small Intestine ◽  
Transport Studies

The elemental composition of amino acids is similar to that of the major structural components of the epithelial cells of the small intestine and other tissues. Therefore, their subcellular localization and concentration measurements are not possible by x-ray microanalysis. Radioactive isotope labeling: I131-tyrosine, Se75-methionine and S35-methionine have been successfully employed in numerous absorption and transport studies. The latter two have been utilized both in vitro and vivo, with similar results in the hamster and human small intestine. Non-radioactive Selenomethionine, since its absorption/transport behavior is assumed to be the same as that of Se75- methionine and S75-methionine could serve as a compound tracer for this amino acid.

Immunoelectron microscope detection of C-type natriuretic peptide in normal human atrial tissue

1993 ◽  
Vol 51 ◽  
pp. 388-389
Author(s):  
Chi-Ming Wei ◽  
Margaret Hukee ◽  
Christopher G.A. McGregor ◽  
John C. Burnett
Keyword(s):  
Amino Acid ◽  
Natriuretic Peptide ◽  
Vascular Tone ◽  
Cardiac Tissue ◽  
Ring Structure ◽  
Terminal Amino Acid ◽  
Amino Acid Peptide ◽  
Normal Human ◽  
Terminal Amino ◽  
The Brain

C-type natriuretic peptide (CNP) is a newly identified peptide that is structurally related to atrial (ANP) and brain natriuretic peptide (BNP). CNP exists as a 22-amino acid peptide and like ANP and BNP has a 17-amino acid ring formed by a disulfide bond. Unlike these two previously identified cardiac peptides, CNP lacks the COOH-terminal amino acid extension from the ring structure. ANP, BNP and CNP decrease cardiac preload, but unlike ANP and BNP, CNP is not natriuretic. While ANP and BNP have been localized to the heart, recent investigations have failed to detect CNP mRNA in the myocardium although small concentrations of CNP are detectable in the porcine myocardium. While originally localized to the brain, recent investigations have localized CNP to endothelial cells consistent with a paracrine role for CNP in the control of vascular tone. While CNP has been detected in cardiac tissue by radioimmunoassay, no studies have demonstrated CNP localization in normal human heart by immunoelectron microscopy.

Amino Acid Metabolism

1979 ◽  
Vol 7 (1) ◽  
pp. 261-262
Author(s):  
E. V. ROWSELL
Keyword(s):  
Amino Acid ◽  
Amino Acid Metabolism ◽  
Acid Metabolism
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