Selective SecA Association with Signal Sequences in Ribosome-bound Nascent Chains

Karamyshev, Andrey L.; Johnson, Arthur E.

doi:10.1074/jbc.m509100200

Cited by 47 publications

(23 citation statements)

References 58 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…4 The incompatibility between the results obtained in vivo and in vitro suggests that any interaction between a novel factor and EspP SP is unstable in cell extracts. Biochemical studies have suggested that SecA can interact with signal peptides that have a highly basic N region at an early stage of translation (15,38), but because EspP(-6) SP (which contains an uncharged N region) promotes post-translational targeting, it does not appear likely that SecA recognizes EspP SP .…”

Section: Discussionmentioning

confidence: 99%

“…TF binding promotes posttranslational targeting, possibly by sterically hindering the docking of ribosomes onto the Sec complex (12)(13)(14). Recent evidence suggests that SecA, a cytoplasmic ATPase that plays a central role in the translocation reaction, may also bind to short nascent presecretory proteins (13,15). Other chaperones such as SecB bind to presecretory proteins late during translation or after translation is complete (16).…”

mentioning

confidence: 99%

See 1 more Smart Citation

An Unusual Signal Peptide Extension Inhibits the Binding of Bacterial Presecretory Proteins to the Signal Recognition Particle, Trigger Factor, and the SecYEG Complex

Peterson

Szabady²,

Bernstein

2006

Journal of Biological Chemistry

View full text Add to dashboard Cite

Considerable evidence indicates that the Escherichia coli signal recognition particle (SRP) selectively targets proteins that contain highly hydrophobic signal peptides to the SecYEG complex cotranslationally. Presecretory proteins that contain only moderately hydrophobic signal peptides typically interact with trigger factor (TF) and are targeted post-translationally. Here we describe a striking exception to this rule that has emerged from the analysis of an unusual 55-amino acid signal peptide associated with the E. coli autotransporter EspP. The EspP signal peptide consists of a C-terminal domain that resembles a classical signal peptide plus an N-terminal extension that is conserved in other autotransporter signal peptides. Although a previous study showed that proteins containing the C-terminal domain of the EspP signal peptide are targeted cotranslationally by SRP, we found that proteins containing the full-length signal peptide were targeted post-translationally via a novel TF-independent mechanism. Mutation of an invariant asparagine residue in the N-terminal extension, however, restored cotranslational targeting. Remarkably, proteins containing extremely hydrophobic derivatives of the EspP signal peptide were also targeted post-translationally. These and other results suggest that the N-terminal extension alters the accessibility of the signal peptide to SRP and TF and promotes post-translational export by reducing the efficiency of the interaction between the signal peptide and the SecYEG complex. Based on data, we propose that the N-terminal extension mediates an interaction with an unidentified cytoplasmic factor or induces the formation of an unusual signal peptide conformation prior to the onset of protein translocation.

show abstract

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

An Unusual Signal Peptide Extension Inhibits the Binding of Bacterial Presecretory Proteins to the Signal Recognition Particle, Trigger Factor, and the SecYEG Complex

Peterson

Szabady²,

Bernstein

2006

Journal of Biological Chemistry

View full text Add to dashboard Cite

show abstract

“…The C-terminal domain is positioned in the middle of the molecule and provides the primary binding site for the nascent chain. The main contact of TF with the ribosome involves residues [44][45][46], located in the binding loop of the N-domain, and ribosomal protein L23 (6). The second contact involves ribosomal protein L29, which is not essential for TF-ribosome interaction (6).…”

mentioning

confidence: 99%

Versatility of Trigger Factor Interactions with Ribosome-Nascent Chain Complexes

Lakshmipathy

Gupta²,

Pinkert

et al. 2010

Journal of Biological Chemistry

View full text Add to dashboard Cite

Trigger factor (TF) is the first molecular chaperone that interacts with nascent chains emerging from bacterial ribosomes. TF is a modular protein, consisting of an N-terminal ribosome binding domain, a PPIase domain, and a C-terminal domain, all of which participate in polypeptide binding. To directly monitor the interactions of TF with nascent polypeptide chains, TF variants were site-specifically labeled with an environmentally sensitive NBD fluorophore. We found a marked increase in TF-NBD fluorescence during translation of firefly luciferase (Luc) chains, which expose substantial regions of hydrophobicity, but not with nascent chains lacking extensive hydrophobic segments. TF remained associated with Luc nascent chains for 111 ؎ 7 s, much longer than it remained bound to the ribosomes (t1 ⁄ 2 ϳ 10 -14 s). Thus, multiple TF molecules can bind per nascent chain during translation. The Escherichia coli cytosolic proteome was classified into predicted weak and strong interactors for TF, based on the occurrence of continuous hydrophobic segments in the primary sequence. The residence time of TF on the nascent chain generally correlated with the presence of hydrophobic regions and the capacity of nascent chains to bury hydrophobicity. Interestingly, TF bound the signal sequence of a secretory protein, pOmpA, but not the hydrophobic signal anchor sequence of the inner membrane protein FtsQ. On the other hand, proteins lacking linear hydrophobic segments also recruited TF, suggesting that TF can recognize hydrophobic surface features discontinuous in sequence. Moreover, TF retained significant affinity for the folded domain of the positively charged, ribosomal protein S7, indicative of an alternative mode of TF action. Thus, unlike other chaperones, TF appears to employ multiple mechanisms to interact with a wide range of substrate proteins.

show abstract

“…It is also interesting to note that the SecA mutation also resulted in the overproduction of 30S and 50S ribosomal proteins. The biological relevance of this observation is not clear considering that the binding of SecA to the L23 ribosomal protein seems to be the only interaction between this protein and the ribosome that has been described (68). Equally unclear is the apparent association of ribosomal proteins with the outer membrane fraction, a phenomenon we believe is not due solely to fraction contamination since we did not observe it when we used the same experimental approach to study the effect of iron on protein synthesis in the same A. baumannii strain (41).…”

Section: Discussionmentioning

confidence: 91%

Role of the Carboxy Terminus of SecA in Iron Acquisition, Protein Translocation, and Virulence of the Bacterial Pathogen Acinetobacter baumannii

et al. 2015

View full text Add to dashboard Cite

Acinetobacter baumannii is a Gram-negative opportunistic nosocomial pathogen that causes pneumonia and soft tissue and systemic infections. Screening of a transposon insertion library of A. baumannii ATCC 19606 T resulted in the identification of the 2010 derivative, which, although capable of growing well in iron-rich media, failed to prosper under iron chelation. Genetic, molecular, and functional assays showed that 2010's iron utilization-deficient phenotype is due to an insertion within the 3= end of secA, which results in the production of a C-terminally truncated derivative of SecA. SecA plays a critical role in protein translocation through the SecYEG membrane channel. Accordingly, the secA mutation resulted in undetectable amounts of the ferric acinetobactin outer membrane receptor protein BauA while not affecting the production of other acinetobactin membrane protein transport components, such as BauB and BauE, or the secretion of acinetobactin by 2010 cells cultured in the presence of subinhibitory concentrations of the synthetic iron chelator 2,2=-dipyridyl. Outer membrane proteins involved in nutrient transport, adherence, and biofilm formation were also reduced in 2010. The SecA truncation also increased production of 30 different proteins, including proteins involved in adaptation/tolerance responses. Although some of these protein changes could negatively affect the pathobiology of the 2010 derivative, its virulence defect is mainly due to its inability to acquire iron via the acinetobactin-mediated system. These results together indicate that although the C terminus of the A. baumannii ATCC 19606 T SecA is not essential for viability, it plays a critical role in the production and translocation of different proteins and virulence.

show abstract

Selective SecA Association with Signal Sequences in Ribosome-bound Nascent Chains

Cited by 47 publications

References 58 publications

An Unusual Signal Peptide Extension Inhibits the Binding of Bacterial Presecretory Proteins to the Signal Recognition Particle, Trigger Factor, and the SecYEG Complex

An Unusual Signal Peptide Extension Inhibits the Binding of Bacterial Presecretory Proteins to the Signal Recognition Particle, Trigger Factor, and the SecYEG Complex

Versatility of Trigger Factor Interactions with Ribosome-Nascent Chain Complexes

Role of the Carboxy Terminus of SecA in Iron Acquisition, Protein Translocation, and Virulence of the Bacterial Pathogen Acinetobacter baumannii

Contact Info

Product

Resources

About