scholarly journals Molecular components of the signal sequence that function in the initiation of protein export.

1982 ◽  
Vol 95 (3) ◽  
pp. 689-696 ◽  
Author(s):  
S D Emr ◽  
T J Silhavy
Keyword(s):  
Amino Acids ◽  
Signal Sequence ◽  
Protein Localization ◽  
Helical Conformation ◽  
Hydrophobic Core ◽  
Selection Procedures ◽  
Sequence Characterization ◽  
Mutant Strains ◽  
Molecular Components

We are studying the mechanism by which the LamB protein is exported to the outer membrane of Escherichia coli. Using two selection procedures based on gene fusions, we have identified a number of mutations that cause alterations in the LamB signal sequence. Characterization of the mutant strains revealed that although many such mutations block LamB export to greater than 95%, others have essentially no effect. These results allow an analysis of the functions performed by the various molecular components of the signal sequence. Our results suggest that a critical subset of four amino acids is contained within the central hydrophobic core of the LamB signal sequence. If this core can assume an alpha-helical conformation, these four amino acids comprise a recognition site that interacts with a component of the cellular export machinery. Since mechanisms of protein localization appear to have been conserved during evolution, the principles established by these results should be applicable to similar studies in eukaryotic cells.

Discovery of functional motifs in h-regions of trypanosome signal sequences

2010 ◽  
Vol 426 (2) ◽  
pp. 135-145 ◽  
Author(s):  
Josh Duffy ◽  
Bhargavi Patham ◽  
Kojo Mensa-Wilmot
Keyword(s):  
Amino Acids ◽  
Signal Sequence ◽  
Bioinformatic Analysis ◽  
Surface Glycoprotein ◽  
Secretory Proteins ◽  
Signal Peptides ◽  
Hydrophobic Core ◽  
Signal Sequences ◽  
Peptide Motifs ◽  
Physiological Relevance

N-terminal signal peptides direct secretory proteins into the ER (endoplasmic reticulum) of eukaryotes or the periplasmic space of prokaryotes. A hydrophobic core (h-region) is important for signal sequence function; however, the mechanism of h-region action is not resolved. To gain new insight into signal sequences, bioinformatic analysis of h-regions from humans, Saccharomyces cerevisiae, Trypanosoma brucei and Escherichia coli was performed. Each species contains a unique set of peptide motifs (h-motifs) characterized by identity components (i.e. sequence of conserved amino acids) joined by spacers. Human h-motifs have four identity components, whereas those from the other species utilize three identity components. Example of h-motifs are human Hs3 {L-x(2)-[AGILPV]-L-x(0,2)-L}, S. cerevisiae Sc1 [L-x(0,2)-S-x(0,3)-A], T. brucei Tb2 {L-x(1,2)-L-[AILV]} and E. coli Ec1 [A-x(0,2)-L-x(0,3)-A]. The physiological relevance of h-motifs was tested with a T. brucei microsomal system for translocation of a VSG (variant surface glycoprotein)-117 signal peptide. Disruption of h-motifs by scrambling of sequences in h-regions produced defective signal peptides, although the hydrophobicity of the peptide was not altered. We conclude that: (i) h-regions harbour h-motifs, and are not random hydrophobic amino acids; (ii) h-regions from different species contain unique sets of h-motifs; and (iii) h-motifs contribute to the biological activity of ER signal peptides. h-Regions are ‘scaffolds’ in which functional h-motifs are embedded. A hypothetical model for h-motif interactions with a Sec61p protein translocon is presented.

Characterization of a human colonic cDNA encoding a structurally novel urea transporter, hUT-A6

2004 ◽  
Vol 287 (4) ◽  
pp. C1087-C1093 ◽  
Author(s):  
Craig P. Smith ◽  
Elizabeth A. Potter ◽  
Robert A. Fenton ◽  
Gavin S. Stewart
Keyword(s):  
Amino Acids ◽  
Alternative Splicing ◽  
Protein Kinase ◽  
Protein Kinase A ◽  
Colonic Mucosa ◽  
Stop Codon ◽  
Hydrophobic Core ◽  
Urea Transporter ◽  
Kinase A

Two closely related genes, UT-A ( Slc14a2) and UT-B ( Slc14a1), encode specialized transporter proteins that modulate the movement of urea across cell membranes. In this article, we report the characterization of a cDNA isolated from human colonic mucosa encoding a novel UT-A urea transporter, hUT-A6. The encoded protein is 235 amino acids (aa) in length, making it the smallest UT-A member characterized. On the basis of previous structural predictions, hUT-A6 is structurally unique in that it consists of a single hydrophobic core flanked by hydrophilic NH2- and COOH-terminal domains. The transcript encoding hUT-A6 contains a novel 129-bp exon, exon 5a, which, as a result of alternative splicing, introduces a unique 19-aa segment and a stop codon. Functionally, the protein transports urea, and this activity is inhibited by phloretin. Interestingly, despite the lack of a protein kinase A (PKA) consensus site {[RK]( 2 )-X-[ST]}, transport of urea by hUT-A6 is stimulated by PKA agonists. Deletion of the two PKA consensus sites from murine UT-A3 (mUT-A3) did not affect the stimulatory response of PKA agonists, which, together with the lack of PKA consensus sites in hUT-A6, indicates that regulation of hUT-A6 and mUT-A3 is not mediated through a classic PKA phosphorylation consensus.

scholarly journals Cloning and characterization of a cDNA for murine macrophage inflammatory protein (MIP), a novel monokine with inflammatory and chemokinetic properties.

1988 ◽  
Vol 167 (6) ◽  
pp. 1939-1944 ◽  
Author(s):  
G Davatelis ◽  
P Tekamp-Olson ◽  
S D Wolpe ◽  
K Hermsen ◽  
C Luedke ◽  
...  
Keyword(s):  
Sequence Data ◽  
Signal Sequence ◽  
Sequence Similarity ◽  
Alpha Helix ◽  
Phage Library ◽  
Hydrophobic Core ◽  
Inflammatory Protein ◽  
Characteristic Signal ◽  
Macrophage Inflammatory Protein

In the course of studies on cachectin/TNF being conducted in our laboratory, a novel macrophage product has been detected and characterized. Termed macrophage inflammatory protein or MIP, this protein appears to be an endogenous mediator of the inflammatory events induced by endotoxin. A cDNA cloned probe for this protein has been isolated from a lambda gt10 phage library prepared from poly(A)+ RNA obtained of endotoxin-induced RAW264.7 cells. The sequence codes for a 92 amino acid-long polypeptide, of which 69 amino acids correspond to the mature product. The sequence predicts a molecular weight of 7,889 and structural analysis of the protein indicates a characteristic signal sequence alpha-helix and a hydrophobic core. Sequence data also confirm no sequence similarity to any other protein listed in the Dayhoff data base.

Whole-Genome Sequence Characterization of Primary Auxin-Responsive Aux/IAA Gene Family in Sorghum (Sorghum bicolor L.)

2010 ◽  
Vol 36 (4) ◽  
pp. 688-694
Author(s):  
Yi-Jun WANG ◽  
Yan-Ping LÜ ◽  
Qin XIE ◽  
De-Xiang DENG ◽  
Yun-Long BIAN
Keyword(s):  
Sorghum Bicolor ◽  
Gene Family ◽  
Genome Sequence ◽  
Whole Genome Sequence ◽  
Whole Genome ◽  
Sequence Characterization ◽  
I Gene

Post-proline endopeptidase, further characterization of the enzyme from pig kidneys

1984 ◽  
Vol 49 (8) ◽  
pp. 1846-1853 ◽  
Author(s):  
Karel Hauzer ◽  
Tomislav Barth ◽  
Linda Servítová ◽  
Karel Jošt
Keyword(s):  
Amino Acids ◽  
Aspartic Acid ◽  
Ion Exchange Chromatography ◽  
Exchange Chromatography ◽  
Relative Molecular Mass ◽  
Enzyme Molecule ◽  
Thiol Compounds ◽  
Modified Method ◽  
N Terminus

A post-proline endopeptidase (EC 3.4.21.26) was isolated from pig kidneys using a modified method described earlier. The enzyme was further purified by ion exchange chromatography on DEAE-Sephacel. The final product contained about 95% of post-proline endopeptidase. The enzyme molecule consisted of one peptide chain with a relative molecular mass of 65 600 to 70 000, containing a large proportion of acidic and alifatic amino acids (glutamic acid, aspartic acid and leucine) and the N-terminus was formed by aspartic acid or asparagine. In order to prevent losses of enzyme activity, thiol compounds has to be added.

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