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PTGR2 catalyzes an NADPH-dependent reduction of the conjugated α,β-unsaturated double bond of 15-keto-PGE 2 , a key step in terminal inactivation of prostaglandins and suppression of PPARγ-mediated adipocyte differentiation. Selective inhibition of PTGR2 may contribute to the improvement of insulin sensitivity with fewer side effects. PTGR2 belongs to the medium-chain dehydrogenase/reductase...
P pili are important adhesive fibers involved in kidney infection by uropathogenic Escherichia coli. Pilus subunits are characterized by a large groove resulting from lack of a β strand. Polymerization of pilus subunits occurs via the donor-strand exchange (DSE) mechanism initiated when the N terminus of an incoming subunit interacts with the P5 region/pocket of the previously assembled subunit groove...
Most eukaryotic pre-mRNAs contain non-coding sequences (introns) that must be removed in order to accurately place the coding sequences (exons) in the correct reading frame. This critical regulatory pre-mRNA splicing event is fundamental in development and cancer. It occurs within a mega-Dalton multicomponent machine composed of RNA and proteins, which undergoes dynamic changes in RNA-RNA, RNA-protein,...
The search for an effective method for accurate, automated enzyme-functional annotation of protein sequences of unknown function is, in the minds of many, a Grail quest. Computational chemists, structural biologists, and mechanistic enzymologists now have teamed together to formulate an integrated, stepwise approach to enzyme function annotation (Kalyanaraman et al., 2008).
The Spt4-Spt5 complex is an essential RNA polymerase II elongation factor found in all eukaryotes and important for gene regulation. We report here the crystal structure of Saccharomyces cerevisiae Spt4 bound to the NGN domain of Spt5. This structure reveals that Spt4-Spt5 binding is governed by an acid-dipole interaction between Spt5 and Spt4. Mutations that disrupt this interaction disrupt the complex...
In this issue of Structure, Lu et al. (2008) report results of structural and functional analysis of rotavirus RNA-dependent RNA polymerase, VP1. Based on their analyses of VP1 in RNA free and bound forms, the authors propose a mechanism for coordinated genome packaging and replication.
Human immunodeficiency virus (HIV-1) interaction with the primary receptor, CD4, induces conformational changes in the viral envelope glycoproteins that allow binding to the CCR5 second receptor and virus entry into the host cell. The small molecule NBD-556 mimics CD4 by binding the gp120 exterior envelope glycoprotein, moderately inhibiting virus entry into CD4-expressing target cells and enhancing...
Understanding the DNA recognition and binding by the AbrB-like family of transcriptional regulators is of significant interest since these proteins enable bacteria to elicit the appropriate response to diverse environmental stimuli. Although these “transition-state regulator” proteins have been well characterized at the genetic level, the general and specific mechanisms of DNA binding remain elusive...
Profilins are key regulators of actin dynamics. They sequester actin monomers, forming a pool for rapid polymer formation stimulated by proteins such as formins. Apicomplexan parasites utilize a highly specialized microfilament system for motility and host cell invasion. Their genomes encode only a small number of divergent actin regulators. We present the first crystal structure of an apicomplexan...
The abundance of dynamic and disordered regions in proteins suggests that structural determinants alone may not be sufficient to describe function. Instead, descriptors that account for the dynamic features of the energy landscape populated by the protein ensemble may be required. Here, we show that the thermodynamics of the dynamical complexity that imparts biological function can be largely reconstructed...
To investigate the mechanism of kinesin13-induced microtubule depolymerization, we have calculated a three-dimensional (3D) map of the kinesin13-microtubule ring complex, using cryo-electron microscopy (cryo-EM) and image analysis. An atomic model of the complex was produced by docking the crystal structures of tubulin and a kinesin13 motor domain (MD) into the 3D map. The model reveals a snapshot...
Rotavirus RNA-dependent RNA polymerase VP1 catalyzes RNA synthesis within a subviral particle. This activity depends on core shell protein VP2. A conserved sequence at the 3′ end of plus-strand RNA templates is important for polymerase association and genome replication. We have determined the structure of VP1 at 2.9 Å resolution, as apoenzyme and in complex with RNA. The cage-like enzyme is similar...
A given protein generally has only one native tertiary fold, which is the conformation with the lowest Gibbs free energy. Mad2, a protein involved in the spindle checkpoint, however, has two natively folded states with similar Gibbs free energies. Through binding to its target Cdc20, Mad2 inhibits the multisubunit ubiquitin ligase, the anaphase-promoting complex or cyclosome (APC/C), and delays the...
Even closely homologous proteins often have different crystallization properties and propensities. This observation can be used to introduce an additional dimension into crystallization trials by simultaneous targeting multiple homologs in what we call a “genome pool” strategy. We show that this strategy works because protein physicochemical properties correlated with crystallization success have...
NBD-556 is a class of HIV-1 entry inhibitors that binds HIV-1 surface glycoprotein gp120 and induces conformational changes, which mimic those caused by CD4 binding. Here, Madani et al. (2008) show that NBD-556 binds to the highly conserved “Phe-43 cavity” on gp120.
We have developed a computational approach to aid the assignment of enzymatic function for uncharacterized proteins that uses homology modeling to predict the structure of the binding site and in silico docking to identify potential substrates. We apply this method to proteins in the functionally diverse enolase superfamily that are homologous to the characterized L-Ala-D/L-Glu epimerase from Bacillus...
Deacetylation of nucleosomes by the Rpd3S histone deacetylase along the path of transcribing RNA polymerase II regulates access to DNA, contributing to faithful gene transcription. The association of Rpd3S with chromatin requires its Eaf3 subunit, which binds histone H3 methylated at lysine 36 (H3K36). Eaf3 is also part of NuA4 acetyltransferase that recognizes methylated H3K4. Here we show that Eaf3...
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