To explore the suggestion that alpha-actinin cross-links actin filaments to the microvillar membrane (Mooseker and Tilney, 1975, J. Cell Biol. 67:725--743; Mooseker, 1976, J. Cell Biol. 71-417--433), we have assessed the possible relatedness of alpha-actinin and the brush-border 95-kdalton protein by four independent criteria: antigenicity, mobility on SDS gels, extractability in nonionic deter...

Chaperones help proteins fold in all cellular compartments, and many associate directly with ribosomes, capturing nascent chains to assist their folding and prevent aggregation. In this issue, new data from Koplin et al. (2010. J. Cell Biol. doi: 10.1083/jcb.200910074) and Albanèse et al. (2010. J. Cell Biol. doi: 10.1083/jcb.201001054) suggest that in addition to promoting protein folding, the...

Here, the solution structure of the Rhodobacter sphaeroides core light-harvesting complex beta polypeptide solubilised in chloroform:methanol is presented. The structure, determined by homonuclear NMR spectroscopy and distance geometry, comprises two alpha helical regions (residue -34 to -15 and -11 to +6, using the numbering system in which the conserved histidine residue is numbered zero) joi...

The sorting of proteins to the appropriate compartment is one of the most fundamental cellular processes. We found that in the model organism Caenorhabditis elegans, correct cotranslational endoplasmic reticulum (ER) transport required the suppressor activity of the nascent polypeptide-associated complex (NAC). NAC did not affect the accurate targeting of ribosomes to ER translocons mediated by...

Trigger factor (TF), the first chaperone in eubacteria to encounter the emerging nascent chain, binds to the large ribosomal subunit in the vicinity of the protein exit tunnel opening and forms a sheltered folding space. Here, we present the 3.5-A crystal structure of the physiological complex of the large ribosomal subunit from the eubacterium Deinococcus radiodurans with the N-terminal domain...

Na+,K(+)-ATPase activity in nerve is reduced in rats with streptozotocin-induced diabetes; three different isoforms of the alpha (catalytic) subunit of the enzyme are present in nerve. Using western blot to determine subunit isoform polypeptide levels in sciatic nerve, we found a substantial reduction in alpha 1-isoform polypeptide (88% at 3 weeks, 94% at 8 weeks) after induction of diabetes by...

Secretory proteins are synthesized with a signal sequence that is usually cleaved from the nascent protein during the translocation of the polypeptide chain into the lumen of the endoplasmic reticulum. To determine the fate of a cleaved signal sequence, we used a synchronized in vitro translocation system. We found that the cleaved signal peptide of preprolactin is further processed close to it...

Protein folding in living cells is inherently coupled to protein synthesis and chain elongation. There is considerable evidence that some nascent chains fold into their native structures in a cotranslational manner before release from the ribosome, but, despite its importance, a detailed description of such a process at the atomic level remains elusive. We show here at a residue-specific level ...

As nascent polypeptide chains are synthesized, they pass through a tunnel in the large ribosomal subunit. Interaction between specific nascent chains and the ribosomal tunnel is used to induce translational stalling for the regulation of gene expression. One well-characterized example is the Escherichia coli SecM (secretion monitor) gene product, which induces stalling to up-regulate translatio...