scholarly journals A Synonymous Mutation in Yersinia enterocolitica yopE Affects the Function of the YopE Type III Secretion Signal

2005 ◽  
Vol 187 (2) ◽  
pp. 707-715 ◽  
Author(s):  
Kumaran S. Ramamurthi ◽  
Olaf Schneewind
Keyword(s):  
Amino Acid ◽  
Amino Acid Sequence ◽  
Type Iii Secretion ◽  
Predicted Amino Acid Sequence ◽  
Nucleotide Position ◽  
Reporter Protein ◽  
Single Nucleotide ◽  
Type Iii ◽  
Secretion Signal ◽  
Nucleotide Mutation

ABSTRACT Yersinia spp. inject virulence proteins called Yops into the cytosol of target eukaryotic cells in an effort to evade phagocytic killing via a dedicated protein-sorting pathway termed type III secretion. Previous studies have proposed that, unlike other protein translocation mechanisms, Yops are not recognized as substrates for secretion via a solely proteinaceous signal. Rather, at least some of this information may be encoded within yop mRNA. Herein, we report that the first seven codons of yopE, when fused to the reporter protein neomycin phosphotransferase (Npt), are sufficient for the secretion of YopE1-7-Npt when type III secretion is induced in vitro. Systematic mutagenesis of yopE codons 1 to 7 reveals that, like yopQ, codons 2, 3, 5, and 7 are sensitive to mutagenesis, thereby defining the first empirical similarity between the secretion signals of two type III secreted substrates. Like that of yopQ, the secretion signal of yopE exhibits a bipartite nature. This is manifested by the ability of codons 8 to 15 to suppress point mutations in the minimal secretion signal that change the amino acid specificities of particular codons or that induce alterations in the reading frame. Further, we have identified a single nucleotide position in codon 3 that, when mutated, conserves the predicted amino acid sequence of the YopE1-7-Npt but abrogates secretion of the reporter protein. When introduced into the context of the full-length yopE gene, the single-nucleotide mutation reduces the type III injection of YopE into HeLa cells, even though the predicted amino acid sequence remains the same. Thus, yopE mRNA appears to encode a property that mediates the type III injection of YopE.

scholarly journals Impassable YscP Substrates and Their Impact on the Yersinia enterocolitica Type III Secretion Pathway

2008 ◽  
Vol 190 (18) ◽  
pp. 6204-6216 ◽  
Author(s):  
Kelly E. Riordan ◽  
Joseph A. Sorg ◽  
Bryan J. Berube ◽  
Olaf Schneewind
Keyword(s):  
Type Iii Secretion ◽  
Host Cells ◽  
Block Type ◽  
Reporter Protein ◽  
Secrete Protein ◽  
Protein Substrates ◽  
Type Iii ◽  
Secretion Signal ◽  
Secretion Pathway ◽  
Partial Blockade

ABSTRACT Yersinia type III machines secrete protein substrates across the bacterial envelope and, following assembly of their secretion needles, transport effector Yops into host cells. According to their destination during type III secretion, early, middle, and late secretion substrates can be distinguished; however, the signals and mechanisms whereby these proteins are recognized and transported by the secretion machine are not understood. Here, we examine several hybrids between secretion substrates and the impassable reporter protein glutathione S-transferase (GST). YscP-GST and YopR-GST blocked type III secretion; however, YscF-, YopD-, YopN-, and LcrV-GST did not. Unlike YopR-GST, which can block type III machines only during their assembly, expression of YscP-GST led to an immediate and complete block of all secretion. The secretion signal of YscP was mapped to its first 10 codons or amino acids; however, YscPΔ2-15-GST, lacking this secretion signal, imposed a partial blockade. YscP-GST copurified with the type III ATPase complex (YscN, YscL, and YscQ) and with YscO, suggesting that the association of specific machine components with the impassable substrate may cause the block in type III secretion.

A Single Thymine Nucleotide Deletion Responsible for Congenital Deficiency of Plasmin Inhibitor

2002 ◽  
Vol 88 (07) ◽  
pp. 144-148 ◽  
Author(s):  
Haruhiko Yoshinaga ◽  
Masako Nakahara ◽  
Aya Shibamiya ◽  
Fumie Nakazawa ◽  
Lindsey Miles ◽  
...  
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Amino Acid Sequence ◽  
Family Members ◽  
Predicted Amino Acid Sequence ◽  
Hemorrhagic Diathesis ◽  
Nucleotide Position ◽  
Congenital Deficiency ◽  
Pi Deficiency ◽  
Plasmin Inhibitor

SummaryPlasma plasmin inhibitor (PI) is a physiological inhibitor of plasminmediated fibrinolysis and constitutes a hemostatic component in blood plasma; hence its deficiency results in a severe hemorrhagic diathesis. We have carried out molecular analysis of American family members with congenital PI deficiency, and detected a single thymine deletion at nucleotide position 332 in exon 5. The deletion was found in both alleles of the homozygotes and in one allele of the heterozygotes, and the patterns of restriction fragment length polymorphism created by the mutation in the family members were compatible with their phenotypes. The deletion caused a frameshift leading to an alteration and shortening of the deduced amino acid sequence. The amino acid sequence consists of the first 83 amino acids of the N-terminal sequence of the normal PI and additional new amino acids, resulting in a mutant composed of 94 amino acids in contrast to 464 amino acids of the normal PI. In transient expression analysis, the mutant PI whose molecular size was compatible with the predicted amino acid sequence was detected in the lysates of the cells transfected with the mutated PI expression vector. The mutant PI was retained and underwent progressive degradation within the cells, and was minimally excreted into the media. These data indicate that this mutation is the cause of PI deficiency in this pedigree.

scholarly journals Type III Secretion of the Salmonella Effector Protein SopE Is Mediated via an N-Terminal Amino Acid Signal and Not an mRNA Sequence

2005 ◽  
Vol 187 (5) ◽  
pp. 1559-1567 ◽  
Author(s):  
M. H. Karavolos ◽  
M. Wilson ◽  
J. Henderson ◽  
J. J. Lee ◽  
C. M. A. Khan
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Amino Acid Sequence ◽  
Host Cell ◽  
Type Iii Secretion ◽  
Effector Protein ◽  
Mrna Sequence ◽  
Type Iii ◽  
Amino Terminal ◽  
Terminal Amino

ABSTRACT Type III secretion systems (TTSS) are virulence-associated components of many gram-negative bacteria that translocate bacterial proteins directly from the bacterial cytoplasm into the host cell. The Salmonella translocated effector protein SopE has no consensus cleavable amino-terminal secretion sequence, and the mechanism leading to its secretion through the Salmonella pathogenicity island 1 (SPI-1) TTSS is still not fully understood. There is evidence from other bacteria which suggests that the TTSS signal may reside within the 5′ untranslated region (UTR) of the mRNA of secreted effectors. We investigated the role of the 5′ UTR in the SPI-1 TTSS-mediated secretion of SopE using promoter fusions and obtained data indicating that the mRNA sequence is not involved in the secretion process. To clarify the proteinaceous versus RNA nature of the signal, we constructed frameshift mutations in the amino-terminal region of SopE of Salmonella enterica serovar Typhimurium SL1344. Only constructs with the native amino acid sequence were secreted, highlighting the importance of the amino acid sequence versus the mRNA sequence for secretion. Additionally, we obtained frameshift mutation data suggesting that the first 15 amino acids are important for secretion of SopE independent of the presence of the chaperone binding site. These data shed light on the nature of the signal for SopE secretion and highlight the importance of the amino-terminal amino acids for correct targeting and secretion of SopE via the SPI-1-encoded TTSS during host cell invasion.

scholarly journals Yersinia enterocolitica Type III Secretion: Mutational Analysis of the yopQ Secretion Signal

2002 ◽  
Vol 184 (12) ◽  
pp. 3321-3328 ◽  
Author(s):  
Kumaran S. Ramamurthi ◽  
Olaf Schneewind
Keyword(s):  
Type Iii Secretion ◽  
Mutational Analysis ◽  
Mrna Sequence ◽  
Reporter Protein ◽  
Frameshift Mutations ◽  
Type Iii ◽  
Synonymous Mutations ◽  
Secretion Signal ◽  
Fusion Site ◽  
Necessary And Sufficient

ABSTRACT Pathogenic Yersinia spp. secrete Yop proteins via the type III pathway. yopQ codons 1 to 15 were identified as a signal necessary and sufficient for the secretion of a fused reporter protein. Frameshift mutations that alter codons 2 to 15 with little alteration of yopQ mRNA sequence do not abolish type III transport, suggesting a model in which yopQ mRNA may provide a signal for secretion (D. M. Anderson and O. Schneewind, Mol. Microbiol. 31:1139-1148, 2001). In a recent study, the yopE signal was truncated to codons 1 to 12. All frameshift mutations introduced within the first 12 codons of yopE abolished secretion. Also, multiple synonymous mutations that changed the mRNA sequence of yopE codons 1 to 12 without altering the amino acid sequence did not affect secretion. These results favor a model whereby an N-terminal signal peptide initiates YopE into the type III pathway (S. A. Lloyd et al., Mol. Microbiol. 39:520-531, 2001). It is reported here that codons 1 to 10 of yopQ act as a minimal secretion signal. Further truncation of yopQ, either at codon 10 or at codon 2, abolished secretion. Replacement of yopQ AUG with either of two other start codons, UUG or GUG, did not affect secretion. However, replacement of AUG with CUG or AAA and initiating translation at the fusion site with npt did not permit Npt secretion, suggesting that the translation of yopQ codons 1 to 15 is a prerequisite for secretion. Frameshift mutations of yopQ codons 1 to 10, 1 to 11, and 1 to 12 abolished secretion signaling, whereas frameshift mutations of yopQ codons 1 to 13, 1 to 14, and 1 to 15 did not. Codon changes at yopQ positions 2 and 10 affected secretion signaling when placed within the first 10 codons but had no effect when positioned in the larger fusion of yopQ codons 1 to 15. An mRNA mutant of yopQ codons 1 to 10, generated by a combination of nine synonymous mutations, was defective in secretion signaling, suggesting that the YopQ secretion signal is not proteinaceous. A model is discussed whereby the initiation of YopQ polypeptide into the type III pathway is controlled by properties of yopQ mRNA.

scholarly journals Structural Characterization of the N Terminus of IpaC from Shigella flexneri

2003 ◽  
Vol 71 (3) ◽  
pp. 1255-1264 ◽  
Author(s):  
Amanda T. Harrington ◽  
Patricia D. Hearn ◽  
Wendy L. Picking ◽  
Jeffrey R. Barker ◽  
Andrew Wessel ◽  
...  
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Type Iii Secretion ◽  
Shigella Flexneri ◽  
Binding Domain ◽  
Host Cells ◽  
Type Iii ◽  
Secretion Signal ◽  
N Terminus ◽  
Chaperone Binding

ABSTRACT The primary effector for Shigella invasion of epithelial cells is IpaC, which is secreted via a type III secretion system. We recently reported that the IpaC N terminus is required for type III secretion and possibly other functions. In this study, mutagenesis was used to identify an N-terminal secretion signal and to determine the functional importance of the rest of the IpaC N terminus. The 15 N-terminal amino acids target IpaC for secretion by Shigella flexneri, and placing additional amino acids at the N terminus does not interfere with IpaC secretion. Furthermore, amino acid sequences with no relationship to the native IpaC secretion signal can also direct its secretion. Deletions introduced beyond amino acid 20 have no effect on secretion and do not adversely affect IpaC function in vivo until they extend beyond residue 50, at which point invasion function is completely eliminated. Deletions introduced at amino acid 100 and extending toward the N terminus reduce IpaC's invasion function but do not eliminate it until they extend to the N-terminal side of residue 80, indicating that a region from amino acid 50 to 80 is critical for IpaC invasion function. To explore this further, the ability of an IpaC N-terminal peptide to associate in vitro with its translocon partner IpaB and its chaperone IpgC was studied. The N-terminal peptide binds tightly to IpaB, but the IpaC central hydrophobic region also appears to participate in this binding. The N-terminal peptide also associates with the chaperone IpgC and IpaB is competitive for this interaction. Based on additional biophysical data, we propose that a region between amino acids 50 and 80 is required for chaperone binding, and that the IpaB binding domain is located downstream from, and possibly overlapping, this region. From these data, we propose that the secretion signal, chaperone binding region, and IpaB binding domain are located at the IpaC N terminus and are essential for presentation of IpaC to host cells during bacterial entry; however, IpaC effector activity may be located elsewhere.

Paris I Dysfibrinogenemia: A Point Mutation in Intron 8 Results in Insertion of a 15 Amino Acid Sequence in the Fibrinogen γ-Chain

1993 ◽  
Vol 69 (03) ◽  
pp. 217-220 ◽  
Author(s):  
Jonathan B Rosenberg ◽  
Peter J Newman ◽  
Michael W Mosesson ◽  
Marie-Claude Guillin ◽  
David L Amrani
Keyword(s):  
Amino Acid ◽  
Amino Acid Sequence ◽  
Point Mutation ◽  
Genomic Dna ◽  
Comparative Sequence Analysis ◽  
Chain Gene ◽  
Molecular Defect ◽  
Nucleotide Position ◽  
Normal Individuals ◽  
Polymerase Chain

SummaryParis I dysfibrinogenemia results in the production of a fibrinogen molecule containing a functionally abnormal γ-chain. We determined the basis of the molecular defect using polymerase chain reaction (PCR) to amplify the γ-chain region of the Paris I subject’s genomic DNA. Comparative sequence analysis of cloned PCR segments of normal and Paris I genomic DNA revealed only an A→G point mutation occurring at nucleotide position 6588 within intron 8 of the Paris I γ-chain gene. We examined six normal individuals and found only normal sequence in this region, indicating that this change is not likely to represent a normal polymorphism. This nucleotide change leads to a 45 bp fragment being inserted between exons 8 and 9 in the mature γparis I chain mRNA, and encodes a 15 amino acid insert after γ350 [M-C-G-E-A-L-P-M-L-K-D-P-C-Y]. Alternative splicing of this region from intron 8 into the mature Paris I γ-chain mRNA also results after translation into a substitution of S for G at position γ351. Biochemical studies of 14C-iodoacetamide incorporation into disulfide-reduced Paris I and normal fibrinogen corroborated the molecular biologic predictions that two additional cysteine residues exist within the γpariS I chain. We conclude that the insertion of this amino acid sequence leads to a conformationallyaltered, and dysfunctional γ-chain in Paris I fibrinogen.

Conserved DNA binding and self-association domains of the Drosophila zeste protein

1992 ◽  
Vol 12 (2) ◽  
pp. 598-608
Author(s):  
J D Chen ◽  
C S Chan ◽  
V Pirrotta
Keyword(s):  
Amino Acid ◽  
Dna Binding ◽  
Amino Acid Sequence ◽  
Coiled Coil ◽  
Helical Structure ◽  
Binding Activity ◽  
Binding Domain ◽  
Drosophila Virilis ◽  
Predicted Amino Acid Sequence ◽  
Dna Binding Domain

The zeste gene product is involved in two types of genetic effects dependent on chromosome pairing: transvection and the zeste-white interaction. Comparison of the predicted amino acid sequence with that of the Drosophila virilis gene shows that several blocks of amino acid sequence have been very highly conserved. One of these regions corresponds to the DNA binding domain. Site-directed mutations in this region indicate that a sequence resembling that of the homeodomain DNA recognition helix is essential for DNA binding activity. The integrity of an amphipathic helical region is also essential for binding activity and is likely to be responsible for dimerization of the DNA binding domain. Another very strongly conserved domain of zeste is the C-terminal region, predicted to form a long helical structure with two sets of heptad repeats that constitute two long hydrophobic ridges at opposite ends and on opposite faces of the helix. We show that this domain is responsible for the extensive aggregation properties of zeste that are required for its role in transvection phenomena. A model is proposed according to which the hydrophobic ridges induce the formation of open-ended coiled-coil structures holding together many hundreds of zeste molecules and possibly anchoring these complexes to other nuclear structures.

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