scholarly journals Mutational Analysis of Xanthomonas Harpin HpaG Identifies a Key Functional Region That Elicits the Hypersensitive Response in Nonhost Plants

2004 ◽  
Vol 186 (18) ◽  
pp. 6239-6247 ◽  
Author(s):  
Jung-Gun Kim ◽  
Eunkyung Jeon ◽  
Jonghee Oh ◽  
Jae Sun Moon ◽  
Ingyu Hwang
Keyword(s):  
Amino Acid ◽  
Hypersensitive Response ◽  
Mutational Analysis ◽  
Site Directed Mutagenesis ◽  
Directed Mutagenesis ◽  
Amino Acid Residues ◽  
Tobacco Plants ◽  
Functional Region ◽  
Amino Acid Peptide ◽  
Α Helix

ABSTRACT HpaG is a type III-secreted elicitor protein of Xanthomonas axonopodis pv. glycines. We have determined the critical amino acid residues important for hypersensitive response (HR) elicitation by random and site-directed mutagenesis of HpaG and its homolog XopA. A plasmid clone carrying hpaG was mutagenized by site-directed mutagenesis, hydroxylamine mutagenesis, and error-prone PCR. A total of 52 mutants were obtained, including 51 single missense mutants and 1 double missense mutant. The HR elicitation activity was abolished in the two missense mutants [HpaG(L50P) and HpaG(L43P/L50P)]. Seven single missense mutants showed reduced activity, and the HR elicitation activity of the rest of the mutants was similar to that of wild-type HpaG. Mutational and deletion analyses narrowed the region essential for elicitor activity to the 23-amino-acid peptide (H2N-NQGISEKQLDQLLTQLIMALLQQ-COOH). A synthetic peptide of this sequence possessed HR elicitor activity at the same concentration as the HpaG protein. This region has 78 and 74% homology with 23- and 27-amino-acid regions of the HrpW harpin domains, respectively, from Pseudomonas and Erwinia spp. The secondary structure of the peptide is predicted to be an α-helix, as is the HrpW region that is homologous to HpaG. The predicted α-helix of HpaG is probably critical for the elicitation of the HR in tobacco plants. In addition, mutagenesis of a xopA gene yielded two gain-of-function mutants: XopA(F48L) and XopA(F48L/M52L). These results indicate that the 12 amino acid residues between L39 and L50 of HpaG have critical roles in HR elicitation in tobacco plants.

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.

Identification of Amino Acid Residues Underlying the Antiport Mechanism of the Mitochondrial Carnitine/Acylcarnitine Carrier by Site-Directed Mutagenesis and Chemical Labeling

Biochemistry ◽  
2014 ◽  
Vol 53 (44) ◽  
pp. 6924-6933 ◽  
Author(s):  
Nicola Giangregorio ◽  
Lara Console ◽  
Annamaria Tonazzi ◽  
Ferdinando Palmieri ◽  
Cesare Indiveri
Keyword(s):  
Amino Acid ◽  
Site Directed Mutagenesis ◽  
Directed Mutagenesis ◽  
Amino Acid Residues ◽  
Chemical Labeling

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.

Activity modulation of the oligopeptidase B from Serratia proteamaculans by site-directed mutagenesis of amino acid residues surrounding catalytic triad histidine

Biochimie ◽  
2017 ◽  
Vol 139 ◽  
pp. 125-136 ◽  
Author(s):  
Anna G. Mikhailova ◽  
Tatiana V. Rakitina ◽  
Vladimir I. Timofeev ◽  
David M. Karlinsky ◽  
Dmitry A. Korzhenevskiy ◽  
...  
Keyword(s):  
Amino Acid ◽  
Catalytic Triad ◽  
Site Directed Mutagenesis ◽  
Directed Mutagenesis ◽  
Amino Acid Residues ◽  
Serratia Proteamaculans ◽  
Oligopeptidase B

scholarly journals Activation of Ha-ras p21 by substitution, deletion, and insertion mutations.

1985 ◽  
Vol 5 (8) ◽  
pp. 1809-1813 ◽  
Author(s):  
R G Chipperfield ◽  
S S Jones ◽  
K M Lo ◽  
R A Weinberg
Keyword(s):  
Amino Acid ◽  
Point Mutations ◽  
Normal Function ◽  
Site Directed Mutagenesis ◽  
Directed Mutagenesis ◽  
Amino Acid Residues ◽  
Transforming Activity ◽  
Ras P21 ◽  
Ras Oncogenes ◽  
Insertion Mutations

The transforming activity of naturally arising ras oncogenes results from point mutations that affect residue 12 or 61 of the encoded 21-kilodalton protein (p21). By use of site-directed mutagenesis, we showed that deletions and insertions of amino acid residues in the region of residue 12 are also effective in conferring oncogenic activity on p21. Common to these various alterations is the disruption that they create in this domain of the protein, which we propose results in the inactivation of a normal function of the protein.

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