A protein complex required for signal-sequence-specific sorting and translocation

Wiedmann, Brigitte; Sakai, Hideaki; Davis, Terri A.; Wiedmann, Martin

doi:10.1038/370434a0

Cited by 387 publications

(415 citation statements)

References 30 publications

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“…This study has identified a number of such potential proteins, including amongst them, NAC and RACK1 homologues. NAC binds to the ribosome in the vicinity of the tunnel exit of the large subunit and modulates co-translational targeting of polypeptides (Wiedmann et al, 1994). The peptide mass fingerprints acquired from the protein samples revealed the presence of at least two isoforms of alpha-NAC and the 2-DE gel pattern indicated that they may be post-translationally modified.…”

Section: Discussionmentioning

confidence: 97%

“…These two spots were identified as being a subunit of the hetero-dimeric nascent-polypeptide associated complex (NAC), a protein that has previously been shown to interact with the large subunit of the ribosome (Wiedmann et al, 1994). A further collection of non-ribosomal protein spots on the acidic section of the 2-DE gel was exceptional in that their intensities increased proportional to the increase of the intensities observed for the ribosomal proteins between the crude and the pure 80S fraction (as can be seen in Figure 1), indicating that these proteins might be factors associated with the ribosomal complex.…”

Section: Detecting Proteins That Associate With the Plant Ribosomementioning

confidence: 99%

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High heterogeneity within the ribosomal proteins of the Arabidopsis thaliana 80S ribosome

et al. 2005

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Proteomic studies have addressed the composition of plant chloroplast ribosomes and 70S ribosomes from the unicellular organism Chlamydomonas reinhardtii, but comprehensive characterization of cytoplasmic 80S ribosomes from higher plants has been lacking. We have used two-dimensional gel electrophoresis (2-DE) and mass spectrometry (MS) to analyse the cytoplasmic 80S ribosomes from the model flowering plant Arabidopsis thaliana. Of the 80 ribosomal protein families predicted to comprise the cytoplasmic 80S ribosome, we have confirmed the presence of 61; specifically, 27 (84%) of the small 40S subunit and 34 (71%) of the large 60S subunit. Nearly half (45%) of the ribosomal proteins identified are represented by two or more distinct spots in the 2-DE gel indicating that these proteins are either post-translationally modified or present as different isoforms. Consistently, MS-based protein identification revealed that at least one-third (34%) of the identified ribosomal protein families showed expression of two or more family members. In addition, we have identified a number of non-ribosomal proteins that co-migrate with the plant 80S ribosomes during gradient centrifugation suggesting their possible association with the 80S ribosomes. Among them, RACK1 has recently been proposed to be a ribosome-associated protein that promotes efficient translation in yeast. The study, thus provides the basis for further investigation into the function of the other identified non-ribosomal proteins as well as the biological meaning of the various ribosomal protein isoforms.

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Section: Discussionmentioning

confidence: 97%

Section: Detecting Proteins That Associate With the Plant Ribosomementioning

confidence: 99%

High heterogeneity within the ribosomal proteins of the Arabidopsis thaliana 80S ribosome

et al. 2005

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“…Nascent polypeptide associated complex (NAC) heterodimer of αNAC (NACA) and βNAC (BTF3b) is characterized as the first cytosolic factor that binds nascent polypeptides emerging from the ribosome and prevents the peptides from incorrectly binding with other cytosolic factors (Wiedmann et al, 1994). This complex is widely conserved from archaea to human.…”

Section: Introductionmentioning

confidence: 99%

Crystal structures of NAC domains of human nascent polypeptide-associated complex (NAC) and its αNAC subunit

et al. 2010

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Nascent polypeptide associated complex (NAC) and its two isolated subunits, αNAC and βNAC, play important roles in nascent peptide targeting. We determined a 1.9 Å resolution crystal structure of the interaction core of NAC heterodimer and a 2.4 Å resolution crystal structure of αNAC NAC domain homodimer. These structures provide detailed information of NAC heterodimerization and αNAC homodimerization. We found that the NAC domains of αNAC and βNAC share very similar folding despite of their relative low identity of amino acid sequences. Furthermore, different electric charge distributions of the two subunits at the NAC interface provide an explanation to the observation that the heterodimer of NAC complex is more stable than the single subunit homodimer. In addition, we successfully built a βNAC NAC domain homodimer model based on homologous modeling, suggesting that NAC domain dimerization is a general property of the NAC family. These 3D structures allow further studies on structurefunction relationship of NAC.

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“…The resultant translational pause may temporally separate the adjacent regions on the growing nascent polypeptide. Given that proteins can fold cotranslationally with the possible involvement of the ribosome (Phillips, 1966;Baldwin, 1975;Yonath, 1992;Kudlicki et al, 1994;Wiedmann et al, 1994;Brimacombe, 1995), the temporal separation might exert a phenotypic effect on the structural organization of the encoded protein. We show that as much as 70% of the domain boundaries in a set of 37 Escherichia coli proteins with known tertiary structure are coded by slow regions (that encompass slow codons) on mRNA.…”

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confidence: 99%

Ribosome‐mediated translational pause and protein domain organization

1996

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Because regions on the messenger ribonucleic acid differ in the rate at which they are translated by the ribosome and because proteins can fold cotranslationally on the ribosome, a question arises as to whether the kinetics of translation influence the folding events in the growing nascent polypeptide chain. Translationally slow regions were identified on mRNAs for a set of 37 multidomain proteins from Escherichia coli with known three-dimensional structures. The frequencies of individual codons in mRNAs of highly expressed genes from E. coli were taken as a measure of codon translation speed. Analysis of codon usage in slow regions showed a consistency with the experimentally determined translation rates of codons; abundant codons that are translated with faster speeds compared with their synonymous codons were found to be avoided; rare codons that are translated at an unexpectedly higher rate were also found to be avoided in slow regions. The statistical significance of the occurrence of such slow regions on mRNA spans corresponding to the oligopeptide domain termini and linking regions on the encoded proteins was assessed. The amino acid type and the solvent accessibility of the residues coded by such slow regions were also examined. The results indicated that protein domain boundaries that mark higher-order structural organization are largely coded by translationally slow regions on the RNA and are composed of such amino acids that are stickier to the ribosome channel through which the synthesized polypeptide chain emerges into the cytoplasm. The translationally slow nucleotide regions on mRNA possess the potential to form hairpin secondary structures and such structures could further slow the movement of ribosome. The results point to an intriguing correlation between protein synthesis machinery and in vivo protein folding. Examination of available mutagenic data indicated that the effects of some of the reported mutations were consistent with our hypothesis.Keywords: codon usage; domain linkers; peptide channel; protein folding; ribosome; translation The rate of protein translation is nonuniform along the mRNA (Varenne et al., 1984). Ribosomes seem to pause as well as stack at specific regions on mRNA (Chaney & Morris, 1979;Wolin &Walter, 1988;Kim et al., 1991;Kim & Hollingsworth, 1992). Two of the mRNA features that slow the ribosome during translation are the presence of slow codons (Varenne et al., 1984;Bonekamp et al., 1985;Wolin & Walter, 1988) and the formation of higher order nucleotide structures (Chaney & Morris, 1979;Tu et al., 1992). The resultant translational pause may temporally separate the adjacent regions on the growing nascent polypeptide. Given that proteins can fold cotranslationally with the possible involvement of the ribosome (Phillips, 1966;Baldwin, 1975;Yonath, 1992;Kudlicki et al., 1994;Wiedmann et al., 1994;Brimacombe, 1995), the temporal separation might exert a phenotypic effect on the structural organization of the encoded protein. We show that as much as 70% of the do...

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A protein complex required for signal-sequence-specific sorting and translocation

Cited by 387 publications

References 30 publications

High heterogeneity within the ribosomal proteins of the Arabidopsis thaliana 80S ribosome

High heterogeneity within the ribosomal proteins of the Arabidopsis thaliana 80S ribosome

Crystal structures of NAC domains of human nascent polypeptide-associated complex (NAC) and its αNAC subunit

Ribosome‐mediated translational pause and protein domain organization

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