The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
Telomerase is a ribonucleoprotein complex that reverse transcribes a portion of its RNA subunit during the synthesis of G-rich DNA at the 3′ end of each chromosome in most eukaryotes. This activity compensates for the inability of the normal DNA replication machinery to fully replicate chromosome termini. The roles of telomerase in cellular immortality and tumor biology have catalyzed a significant...
Transcription by RNA polymerase II (RNAPII) is a central process in eukaryotic gene regulation. While atomic details exist for the yeast RNAPII, characterization of the human complex lags behind, mostly due to the inability to obtain large quantities of purified material. Although the complexes have the same protein composition and high sequence similarity, understanding of transcription and of transcription-coupled...
Maturation of the bacteriophage HK97 capsid from a precursor (Prohead II) to the mature state (Head II) involves a 60 Å radial expansion. The mature particle is formed by 420 copies of the major capsid protein organized on a T = 7 laevo lattice with each subunit covalently crosslinked to two neighbors. Well-characterized pH 4 expansion intermediates make HK97 valuable for investigating quaternary...
Using self-organized polymer models, we predict mechanical unfolding and refolding pathways of ribozymes, and the green fluorescent protein. In agreement with experiments, there are between six and eight unfolding transitions in the Tetrahymena ribozyme. Depending on the loading rate, the number of rips in the force-ramp unfolding of the Azoarcus ribozymes is between two and four. Force-quench refolding...
Thioredoxin is ubiquitous and regulates various target proteins through disulfide bond reduction. We report the structure of thioredoxin (HvTrxh2 from barley) in a reaction intermediate complex with a protein substrate, barley α-amylase/subtilisin inhibitor (BASI). The crystal structure of this mixed disulfide shows a conserved hydrophobic motif in thioredoxin interacting with a sequence of residues...
The SF3a complex, consisting of SF3a60, SF3a66, and SF3a120, in 17S U2 snRNP is crucial to spliceosomal assembly. SF3a120 contains two tandem SURP domains (SURP1 and SURP2), and SURP2 is responsible for binding to SF3a60. We found that the SURP2 fragment forms a stable complex with an SF3a60 fragment (residues 71–107) and solved its structure by NMR spectroscopy. SURP2 exhibits a fold of the α1-α2-3...
Crystallization remains a critical step in X-ray structure determination. Because it is not generally possible to rationally predict crystallization conditions, commercial screens have been developed which sample a wide range of crystallization space. While this approach has proved successful in many cases, a significant number of proteins fail to crystallize despite being soluble and monodispersed...
A remarkable structure of an 86 kDa substrate encapsulated in a single-ring GroEL/GroES chaperonin complex is revealed by cryo-electron microscopy in this issue of Structure (Chen et al., 2006). Surprisingly, the protein-folding chamber is 80% larger than that of the double-ring GroEL/ES structure.
Bacteriophage ϕ29 requires scaffolding protein to assemble the 450 × 540 Å prolate prohead with T = 3 symmetry end caps. In infections with a temperature-sensitive mutant scaffolding protein, capsids assemble predominantly into 370 Å diameter isometric particles with T = 3 symmetry that lack a head-tail connector. However, a few larger, 430 Å diameter, particles are also assembled. Cryo-electron microscopy...
ABCG2 is a multidrug efflux pump associated with resistance of cancer cells to a plethora of unrelated drugs. ABCG2 is a “half-transporter,” and previous studies have indicated that it forms homodimers and higher oligomeric species. In this manuscript, electron microscopic structural analysis directly addressed this issue. An N-terminal hexahistidine-tagged ABCG2 R482G isoform was expressed...
Electron cryomicroscopy reveals an unprecedented conformation of the single-ring mutant of GroEL (SR398) bound to GroES in the presence of Mg-ATP. This conformation exhibits a considerable expansion of the folding cavity, with ∼80% more volume than the X-ray structure of the equivalent cis cavity in the GroEL-GroES-(ADP) 7 complex. This expanded conformation can encapsulate an 86 kDa heterodimeric...
The recent crystal structure of complement protein component C2a reveals an interface between its VWA and serine protease domains that could not exist in the zymogen C2. The implied change in VWA domain conformation between C2 and C2a differs from that described for other VWA domains, including the I domains in integrins. Here, the remarkable diversity in both conformational regulation and ligand...
With the increased popularity of normal mode analyses in structural biology, it is important to carefully consider how to best utilize the results for gaining biological insights without over interpretation. The discussion in this article argues that for the purpose of identifying correlated motions in biomolecules, a case separate from concomitant conformational changes of structural motifs, it is...
Elastin provides extensible tissues, including arteries and skin, with the propensity for elastic recoil, whereas amyloid fibrils are associated with tissue-degenerative diseases, such as Alzheimer's. Although both elastin-like and amyloid-like materials result from the self-organization of proteins into fibrils, the molecular basis of their differing physical properties is poorly understood. Using...
Several recent papers have applied optical methods to directly visualize the assembly of individual RecA and Rad51 filaments on DNA. The hope is that application of such methods will shed light on the many mysteries that still surround how these remarkable filaments function in genetic recombination.
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.