scholarly journals Characterization of subunit interactions in the hetero-oligomeric retinoid oxidoreductase complex

2021 ◽  
Vol 478 (19) ◽  
pp. 3597-3611
Author(s):  
Mark K. Adams ◽  
Olga V. Belyaeva ◽  
Lizhi Wu ◽  
Ivis F. Chaple ◽  
Katelyn Dunigan-Russell ◽  
...  
Keyword(s):  
Quaternary Structure ◽  
Site Directed Mutagenesis ◽  
Amino Acid Residues ◽  
Subunit Interactions ◽  
Retinol Dehydrogenase ◽  
Cofactor Binding ◽  
All Trans Retinoic Acid ◽  
And Function ◽  
Insight Into

The hetero-oligomeric retinoid oxidoreductase complex (ROC) catalyzes the interconversion of all-trans-retinol and all-trans-retinaldehyde to maintain the steady-state output of retinaldehyde, the precursor of all-trans-retinoic acid that regulates the transcription of numerous genes. The interconversion is catalyzed by two distinct components of the ROC: the NAD(H)-dependent retinol dehydrogenase 10 (RDH10) and the NADP(H)-dependent dehydrogenase reductase 3 (DHRS3). The binding between RDH10 and DHRS3 subunits in the ROC results in mutual activation of the subunits. The molecular basis for their activation is currently unknown. Here, we applied site-directed mutagenesis to investigate the roles of amino acid residues previously implied in subunit interactions in other SDRs to obtain the first insight into the subunit interactions in the ROC. The results of these studies suggest that the cofactor binding to RDH10 subunit is critical for the activation of DHRS3 subunit and vice versa. The C-terminal residues 317–331 of RDH10 are critical for the activity of RDH10 homo-oligomers but not for the binding to DHRS3. The C-terminal residues 291–295 are required for DHRS3 subunit activity of the ROC. The highly conserved C-terminal cysteines appear to be involved in inter-subunit communications, affecting the affinity of the cofactor binding site in RDH10 homo-oligomers as well as in the ROC. Modeling of the ROC quaternary structure based on other known structures of SDRs suggests that its integral membrane-associated subunits may be inserted in adjacent membranes of the endoplasmic reticulum (ER), making the formation and function of the ROC dependent on the dynamic nature of the tubular ER network.

Chitosanase from Streptomyces sp. strain N174: a comparative review of its structure and function

1997 ◽  
Vol 75 (6) ◽  
pp. 687-696 ◽  
Author(s):  
Tamo Fukamizo ◽  
Ryszard Brzezinski
Keyword(s):  
Amino Acid ◽  
Amino Acid Sequence ◽  
Substrate Binding ◽  
Structure And Function ◽  
Site Directed Mutagenesis ◽  
Directed Mutagenesis ◽  
Amino Acid Residues ◽  
Streptomyces Sp ◽  
Binding Cleft ◽  
And Function

Novel information on the structure and function of chitosanase, which hydrolyzes the beta -1,4-glycosidic linkage of chitosan, has accumulated in recent years. The cloning of the chitosanase gene from Streptomyces sp. strain N174 and the establishment of an efficient expression system using Streptomyces lividans TK24 have contributed to these advances. Amino acid sequence comparisons of the chitosanases that have been sequenced to date revealed a significant homology in the N-terminal module. From energy minimization based on the X-ray crystal structure of Streptomyces sp. strain N174 chitosanase, the substrate binding cleft of this enzyme was estimated to be composed of six monosaccharide binding subsites. The hydrolytic reaction takes place at the center of the binding cleft with an inverting mechanism. Site-directed mutagenesis of the carboxylic amino acid residues that are conserved revealed that Glu-22 and Asp-40 are the catalytic residues. The tryptophan residues in the chitosanase do not participate directly in the substrate binding but stabilize the protein structure by interacting with hydrophobic and carboxylic side chains of the other amino acid residues. Structural and functional similarities were found between chitosanase, barley chitinase, bacteriophage T4 lysozyme, and goose egg white lysozyme, even though these proteins share no sequence similarities. This information can be helpful for the design of new chitinolytic enzymes that can be applied to carbohydrate engineering, biological control of phytopathogens, and other fields including chitinous polysaccharide degradation. Key words: chitosanase, amino acid sequence, overexpression system, reaction mechanism, site-directed mutagenesis.

scholarly journals Identification and characterization of amphibian SLC26A5 using RNA-Seq

BMC Genomics ◽  
2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Zhongying Wang ◽  
Qixuan Wang ◽  
Hao Wu ◽  
Zhiwu Huang
Keyword(s):  
Amino Acid ◽  
Inner Ear ◽  
Hair Cells ◽  
Rana Catesbeiana ◽  
Site Directed Mutagenesis ◽  
Amino Acid Residues ◽  
Rna Seq ◽  
American Bullfrog ◽  
Frog Species

Abstract Background Prestin (SLC26A5) is responsible for acute sensitivity and frequency selectivity in the vertebrate auditory system. Limited knowledge of prestin is from experiments using site-directed mutagenesis or domain-swapping techniques after the amino acid residues were identified by comparing the sequence of prestin to those of its paralogs and orthologs. Frog prestin is the only representative in amphibian lineage and the studies of it were quite rare with only one species identified. Results Here we report a new coding sequence of SLC26A5 for a frog species, Rana catesbeiana (the American bullfrog). In our study, the SLC26A5 gene of Rana has been mapped, sequenced and cloned successively using RNA-Seq. We measured the nonlinear capacitance (NLC) of prestin both in the hair cells of Rana’s inner ear and HEK293T cells transfected with this new coding gene. HEK293T cells expressing Rana prestin showed electrophysiological features similar to that of hair cells from its inner ear. Comparative studies of zebrafish, chick, Rana and an ancient frog species showed that chick and zebrafish prestin lacked NLC. Ancient frog’s prestin was functionally different from Rana. Conclusions We mapped and sequenced the SLC26A5 of the Rana catesbeiana from its inner ear cDNA using RNA-Seq. The Rana SLC26A5 cDNA was 2292 bp long, encoding a polypeptide of 763 amino acid residues, with 40% identity to mammals. This new coding gene could encode a functionally active protein conferring NLC to both frog HCs and the mammalian cell line. While comparing to its orthologs, the amphibian prestin has been evolutionarily changing its function and becomes more advanced than avian and teleost prestin.

scholarly journals Structure and function of factor XI

Blood ◽  
2010 ◽  
Vol 115 (13) ◽  
pp. 2569-2577 ◽  
Author(s):  
Jonas Emsley ◽  
Paul A. McEwan ◽  
David Gailani
Keyword(s):  
Catalytic Domain ◽  
Structural Features ◽  
Factor Ix ◽  
Missense Mutations ◽  
Factor Xi ◽  
Disk Structure ◽  
Ligand Binding Sites ◽  
And Function ◽  
Insight Into

AbstractFactor XI (FXI) is the zymogen of an enzyme (FXIa) that contributes to hemostasis by activating factor IX. Although bleeding associated with FXI deficiency is relatively mild, there has been resurgence of interest in FXI because of studies indicating it makes contributions to thrombosis and other processes associated with dysregulated coagulation. FXI is an unusual dimeric protease, with structural features that distinguish it from vitamin K–dependent coagulation proteases. The recent availability of crystal structures for zymogen FXI and the FXIa catalytic domain have enhanced our understanding of structure-function relationships for this molecule. FXI contains 4 “apple domains” that form a disk structure with extensive interfaces at the base of the catalytic domain. The characterization of the apple disk structure, and its relationship to the catalytic domain, have provided new insight into the mechanism of FXI activation, the interaction of FXIa with the substrate factor IX, and the binding of FXI to platelets. Analyses of missense mutations associated with FXI deficiency have provided additional clues to localization of ligand-binding sites on the protein surface. Together, these data will facilitate efforts to understand the physiology and pathology of this unusual protease, and development of therapeutics to treat thrombotic disorders.

scholarly journals Regulation of N-linked core glycosylation: use of a site-directed mutagenesis approach to identify Asn-Xaa-Ser/Thr sequons that are poor oligosaccharide acceptors

1997 ◽  
Vol 323 (2) ◽  
pp. 415-419 ◽  
Author(s):  
Lakshmi KASTURI ◽  
Hegang CHEN ◽  
Susan H. SHAKIN-ESHLEMAN
Keyword(s):  
Amino Acid ◽  
Amino Acid Residue ◽  
Site Directed Mutagenesis ◽  
Directed Mutagenesis ◽  
Amino Acid Residues ◽  
Free Translation ◽  
A Cell ◽  
And Function ◽  
A Site ◽  
The Impact

N-linked glycosylation can profoundly affect protein expression and function. N-linked glycosylation usually occurs at the sequon Asn-Xaa-Ser/Thr, where Xaa is any amino acid residue except Pro. However, many Asn-Xaa-Ser/Thr sequons are glycosylated inefficiently or not at all for reasons that are poorly understood. We have used a site-directed mutagenesis approach to examine how the Xaa and hydroxy (Ser/Thr) amino acid residues in sequons influence core-glycosylation efficiency. We recently demonstrated that certain Xaa amino acids inhibit core glycosylation of the sequon, Asn37-Xaa-Ser, in rabies virus glycoprotein (RGP). Here we examine the impact of different Xaa residues on core-glycosylation efficiency when the Ser residue in this sequon is replaced with Thr. The core-glycosylation efficiencies of RGP variants with different Asn37-Xaa-Ser/Thr sequons were compared by using a cell-free translation/glycosylation system. Using this approach we confirm that four Asn-Xaa-Ser sequons are poor oligosaccharide acceptors: Asn-Trp-Ser, Asn-Asp-Ser, Asn-Glu-Ser and Asn-Leu-Ser. In contrast, Asn-Xaa-Thr sequons are efficiently glycosylated, even when Xaa = Trp, Asp, Glu or Leu. A comparison of the glycosylation status of Asn-Xaa-Ser and Asn-Xaa-Thr sequons in other glycoproteins confirms that sequons with Xaa = Trp, Asp, Glu or Leu are rarely glycosylated when Ser is the hydroxy amino acid residue, and that these sequons are unlikely to serve as glycosylation sites when introduced into proteins by site-directed mutagenesis.

Gene Cloning, Nucleotide Sequencing, and Purification and Characterization of the Low-Specificityl-Threonine Aldolase from Pseudomonas sp. Strain NCIMB 10558

1998 ◽  
Vol 64 (2) ◽  
pp. 549-554 ◽  
Author(s):  
Ji-Quan Liu ◽  
Saeko Ito ◽  
Tohru Dairi ◽  
Nobuya Itoh ◽  
Michihiko Kataoka ◽  
...  
Keyword(s):  
Amino Acid ◽  
Significant Loss ◽  
Site Directed Mutagenesis ◽  
Nucleotide Sequencing ◽  
Predicted Amino Acid Sequence ◽  
Amino Acid Residues ◽  
Purification And Characterization ◽  
Reading Frame ◽  
Threonine Aldolase

ABSTRACT A low-specificity l-threonine aldolase (l-TA) gene from Pseudomonas sp. strain NCIMB 10558 was cloned and sequenced. The gene contains an open reading frame consisting of 1,041 nucleotides corresponding to 346 amino acid residues. The gene was overexpressed in Escherichia colicells, and the recombinant enzyme was purified and characterized. The enzyme, requiring pyridoxal 5′-phosphate as a coenzyme, is strictlyl specific at the α position, whereas it cannot distinguish between threo and erythro forms at the β position. In addition to threonine, the enzyme also acts on various other l-β-hydroxy-α-amino acids, includingl-β-3,4-dihydroxyphenylserine,l-β-3,4-methylenedioxyphenylserine, andl-β-phenylserine. The predicted amino acid sequence displayed less than 20% identity with those of low-specificityl-TA from Saccharomyces cerevisiae,l-allo-threonine aldolase from Aeromonas jandaei, and four relevant hypothetical proteins from other microorganisms. However, lysine 207 of low-specificity l-TA from Pseudomonas sp. strain NCIMB 10558 was found to be completely conserved in these proteins. Site-directed mutagenesis experiments showed that substitution of Lys207 with Ala or Arg resulted in a significant loss of enzyme activity, with the corresponding disappearance of the absorption maximum at 420 nm. Thus, Lys207 of thel-TA probably functions as an essential catalytic residue, forming an internal Schiff base with the pyridoxal 5′-phosphate of the enzyme to catalyze the reversible aldol reaction.

Implications of Stisa2 catalytic residue restoration through site directed mutagenesis

2016 ◽  
Vol 42 (2) ◽  
Author(s):  
Hasnain Hussain ◽  
Nikson Fatt Ming Chong
Keyword(s):  
Catalytic Activity ◽  
Catalytic Triad ◽  
Site Directed Mutagenesis ◽  
Amino Acid Residues ◽  
Qualitative And Quantitative Analysis ◽  
Conserved Residues ◽  
Overlap Extension Pcr ◽  
Overlap Extension ◽  
Catalytic Network ◽  
And Function

AbstractObjective:Restoration of catalytic activity of Isa2 fromMethods:The six conserved amino acid residues absent in the Stisa2 gene were restored by mutation using the overlap extension PCR and the asymmetrical overlap extension PCR methods. Next, mutant Stisa2 with restored catalytic residues was expressed inResults:Both qualitative and quantitative analysis showed that the restoration of the conserved residues in the catalytic site did not restore starch debranching activity. Molecular modeling showed greater than expected distances between the catalytic triad in mutant Stisa2. These additional distances are likely to prevent hydrogen bonding which stabilizes the reaction intermediate, and are critical for catalytic activity.Conclusions:These results suggest that during evolution, mutations in other highly conserved regions have caused significant changes to the structure and function of the catalytic network. Catalytically inactive Isa2, which is conserved in starch-producing plants, has evolved important non-catalytic roles such as in substrate binding and in regulating isoamylase activity.

scholarly journals Characterization of a Novel Bifunctional Dihydropteroate Synthase/Dihydropteroate Reductase Enzyme from Helicobacter pylori

2007 ◽  
Vol 189 (11) ◽  
pp. 4062-4069 ◽  
Author(s):  
Itay Levin ◽  
Moshe Mevarech ◽  
Bruce A. Palfey
Keyword(s):  
Helicobacter Pylori ◽  
Reducing Power ◽  
Site Directed Mutagenesis ◽  
Flavin Mononucleotide ◽  
Amino Acid Residues ◽  
Dihydropteroate Synthase ◽  
Terminal Domain ◽  
Initiation Of Translation ◽  
H Pylori

ABSTRACT Tetrahydrofolate is a ubiquitous C1 carrier in many biosynthetic pathways in bacteria, importantly, in the biosynthesis of formylmethionyl tRNAfMet, which is essential for the initiation of translation. The final step in the biosynthesis of tetrahydrofolate is carried out by the enzyme dihydrofolate reductase (DHFR). A search of the complete genome sequence of Helicobacter pylori failed to reveal any sequence that encodes DHFR. Previous studies demonstrated that the H. pylori dihydropteroate synthase gene folP can complement an Escherichia coli strain in which folA and folM, encoding two distinct DHFRs, are deleted. It was also shown that H. pylori FolP possesses an additional N-terminal domain that binds flavin mononucleotide (FMN). Homologous domains are found in FolP proteins of other microorganisms that do not possess DHFR. In this study, we demonstrated that H. pylori FolP is also a dihydropteroate reductase that derives its reducing power from soluble flavins, reduced FMN and reduced flavin adenine dinucleotide. We also determined the stoichiometry of the enzyme-bound flavin and showed that half of the bound flavin is exchangeable with the soluble flavins. Finally, site-directed mutagenesis of the most conserved amino acid residues in the N-terminal domain indicated the importance of these residues for the activity of the enzyme as a dihydropteroate reductase.

scholarly journals Identification of Residues Important for the Activity ofHaloferax volcaniiAglD, a Component of the Archaeal N-Glycosylation Pathway

Archaea ◽  
2010 ◽  
Vol 2010 ◽  
pp. 1-9 ◽  
Author(s):  
Lina Kaminski ◽  
Jerry Eichler
Keyword(s):  
Biochemical Characterization ◽  
Haloferax Volcanii ◽  
Site Directed Mutagenesis ◽  
Directed Mutagenesis ◽  
Amino Acid Residues ◽  
Natural Substrate ◽  
Identify Amino Acid ◽  
Glycosylation Pathway

InHaloferax volcanii, AglD adds the final hexose to the N-linked pentasaccharide decorating the S-layer glycoprotein. Not knowing the natural substrate of the glycosyltransferase, together with the challenge of designing assays compatible with hypersalinity, has frustrated efforts at biochemical characterization of AglD activity. To circumvent these obstacles, an in vivo assay designed to identify amino acid residues important for AglD activity is described. In the assay, restoration of AglD function in anHfx. volcanii aglDdeletion strain transformed to express plasmid-encoded versions of AglD, generated through site-directed mutagenesis at positions encoding residues conserved in archaeal homologues of AglD, is reflected in the behavior of a readily detectable reporter of N-glycosylation. As such Asp110 and Asp112 were designated as elements of the DXD motif of AglD, a motif that interacts with metal cations associated with nucleotide-activated sugar donors, while Asp201 was predicted to be the catalytic base of the enzyme.

scholarly journals Purification and Characterization of NafY (Apodinitrogenase γ Subunit) fromAzotobacter vinelandii

2004 ◽  
Vol 279 (19) ◽  
pp. 19739-19746 ◽  
Author(s):  
Luis M. Rubio ◽  
Steven W. Singer ◽  
Paul W. Ludden
Keyword(s):  
Biochemical Characterization ◽  
Azotobacter Vinelandii ◽  
Site Directed Mutagenesis ◽  
Cofactor Binding ◽  
Unknown Structure ◽  
Additional Protein ◽  
Epr Signal ◽  
Iron Molybdenum Cofactor ◽  
Very High

The formation of an active dinitrogenase requires the synthesis and the insertion of the iron-molybdenum cofactor (FeMo-co) into a presynthesized apodinitrogenase. InAzotobacter vinelandii, NafY (also known as γ protein) has been proposed to be a FeMo-co insertase because of its ability to bind FeMo-co and apodinitrogenase. Here we report the purification and biochemical characterization of NafY and reach the following conclusions. First, NafY is a 26-kDa monomeric protein that binds one molecule of FeMo-co with very high affinity (Kd≈ 60 nm); second, the NafY-FeMo-co complex exhibits aS= 3/2 EPR signal with features similar to the signals for extracted FeMo-co and the M center of dinitrogenase; third, site-directed mutagenesis ofnafYindicates that the His121residue of NafY is involved in cofactor binding; and fourth, NafY binding to apodinitrogenase or to FeMo-co does not require the presence of any additional protein. In addition, we have obtained evidence that suggests the ability of NafY to bind NifB-co, an FeS cluster of unknown structure that is a biosynthetic precursor to FeMo-co.

Functional analysis of amino acid residues at the dimerisation interface of KpnI DNA methyltransferase

2006 ◽  
Vol 387 (5) ◽  
pp. 515-523 ◽  
Author(s):  
Shivakumara Bheemanaik ◽  
Janusz M. Bujnicki ◽  
Valakunja Nagaraja ◽  
Desirazu N. Rao
Keyword(s):  
Dna Methyltransferase ◽  
Three Dimensional ◽  
Site Directed Mutagenesis ◽  
Amino Acid Residues ◽  
Three Dimensional Model ◽  
Cofactor Binding ◽  
Protein Fold Recognition ◽  
Fluorescence Measurements ◽  
Complete Disruption

AbstractKpnI DNA-(N6-adenine) methyltransferase (M.KpnI) recognises the sequence 5′-GGTACC-3′ and transfers the methyl group fromS-adenosyl-L-methionine (AdoMet) to the N6 position of the adenine residue in each strand. Earlier studies have shown that M.KpnI exists as a dimer in solution, unlike most other MTases. To address the importance of dimerisation for enzyme function, a three-dimensional model of M.KpnI was obtained based on protein fold-recognition analysis, using the crystal structures of M.RsrI and M.MboIIA as templates. Residues I146, I161 and Y167, the side chains of which are present in the putative dimerisation interface in the model, were targeted for site-directed mutagenesis. Methylation andin vitrorestriction assays showed that the mutant MTases are catalytically inactive. Mutation at the I146 position resulted in complete disruption of the dimer. The replacement of I146 led to drastically reduced DNA and cofactor binding. Substitution of I161 resulted in weakening of the interaction between monomers, leading to both monomeric and dimeric species. Steady-state fluorescence measurements showed that the wild-type KpnI MTase induces structural distortion in bound DNA, while the mutant MTases do not. The results establish that monomeric MTase is catalytically inactive and that dimerisation is an essential event for M.KpnI to catalyse the methyl transfer reaction.

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