Redefining the catalytic HECT domain boundaries for the HECT E3 ubiquitin ligase family.

There are 28 unique human members of the homologous to E6AP C-terminus (HECT) E3 ubiquitin ligase family. Each member of the HECT E3 ubiquitin ligases contains a conserved bilobal HECT domain of approximately 350 residues found near their C-termini that is responsible for their respective ubiquitylation activities. Recent studies have begun to elucidate specific roles that each HECT E3 ubiquitin ligase has in various cancers, age-induced neurodegeneration, and neurological disorders.

An Angelman syndrome substitution in the HECT E3 ubiquitin ligase C-terminal Lobe of E6AP affects protein stability and activity.

Angelman syndrome (AS) is a rare neurodevelopmental disorder characterized by speech impairment, intellectual disability, ataxia, and epilepsy. AS is caused by mutations in the maternal copy of UBE3A located on chromosome 15q11-13. UBE3A codes for E6AP (E6 Associated Protein), a prominent member of the HECT (Homologous to E6AP C-Terminus) E3 ubiquitin ligase family.

H, C, and N resonance assignments of the C-terminal lobe of the human HECT E3 ubiquitin ligase ITCH.

ITCH (aka Atrophin-1-interacting protein 4) is a prominent member of the NEDD4 HECT (Homologous to E6AP C-Terminus) E3 ubiquitin ligase family that regulates numerous cellular functions including inflammatory responses through T-cell activation, cell differentiation, and apoptosis. Known intracellular targets of ITCH-dependent ubiquitylation include receptor proteins, signaling molecules, and transcription factors. The HECT C-terminal lobe of ITCH contains the conserved catalytic cysteine required for the covalent attachment of ubiquitin onto a substrate and polyubiquitin chain assembly.

Solution structure of the E3 ligase HOIL-1 Ubl domain.

The E3 ligases HOIL-1 and parkin are each comprised of an N-terminal ubiquitin-like (Ubl) domain followed by a zinc-binding region and C-terminal RING-In-between-RING-RING domains. These two proteins, involved in the ubiquitin-mediated degradation pathway, are the only two known E3 ligases to share this type of multidomain architecture. Further, the Ubl domain of both HOIL-1 and parkin has been shown to interact with the S5a subunit of the 26S proteasome.

Identification of a novel Zn2+-binding domain in the autosomal recessive juvenile Parkinson-related E3 ligase parkin.

Missense mutations in park2, encoding the parkin protein, account for approximately 50% of autosomal recessive juvenile Parkinson disease (ARJP) cases. Parkin belongs to the family of RBR (RING-between-RING) E3 ligases involved in the ubiquitin-mediated degradation and trafficking of proteins such as Pael-R and synphillin-1. The proposed architecture of parkin, based largely on sequence similarity studies, consists of N-terminal ubiquitin-like and C-terminal RBR domains.

Structure of the Parkin in-between-ring domain provides insights for E3-ligase dysfunction in autosomal recessive Parkinson's disease.

Mutations in Parkin are one of the predominant hereditary factors found in patients suffering from autosomal recessive juvenile Parkinsonism. Parkin is a member of the E3 ubiquitin ligase family that is defined by a tripartite RING1-in-between-ring (IBR)-RING2 motif. In Parkin, the IBR domain has been shown to augment binding of the E2 proteins UbcH7 and UbcH8, and the subsequent ubiquitination of the proteins synphilin-1, Sept5, and SIM2.

Functional similarities between phage lambda Orf and Escherichia coli RecFOR in initiation of genetic exchange.

Genetic recombination in bacteriophage lambda relies on DNA end processing by Exo to expose 3'-tailed strands for annealing and exchange by beta protein. Phage lambda encodes an additional recombinase, Orf, which participates in the early stages of recombination by supplying a function equivalent to the Escherichia coli RecFOR complex. These host enzymes assist loading of the RecA strand exchange protein onto ssDNA coated with ssDNA-binding protein.

Crystal structure of bacteriophage lambda cII and its DNA complex.

The tetrameric cII protein from bacteriophage lambda activates transcription from the phage promoters P(RE), P(I), and P(AQ) by binding to two direct repeats that flank the promoter -35 element. Here, we present the X-ray crystal structure of cII alone (2.8 A resolution) and in complex with its DNA operator from P(RE) (1.

The crystal structure of Escherichia coli MoaB suggests a probable role in molybdenum cofactor synthesis.

The crystal structure of Escherichia coli MoaB was determined by multiwavelength anomalous diffraction phasing and refined at 1.6-A resolution. The molecule displayed a modified Rossman fold.

Data mining crystallization databases: knowledge-based approaches to optimize protein crystal screens.

Protein crystallization is a major bottleneck in protein X-ray crystallography, the workhorse of most structural proteomics projects. Because the principles that govern protein crystallization are too poorly understood to allow them to be used in a strongly predictive sense, the most common crystallization strategy entails screening a wide variety of solution conditions to identify the small subset that will support crystal nucleation and growth. We tested the hypothesis that more efficient crystallization strategies could be formulated by extracting useful patterns and correlations from the large data sets of crystallization trials created in structural proteomics projects.

Strategies for structural proteomics of prokaryotes: Quantifying the advantages of studying orthologous proteins and of using both NMR and X-ray crystallography approaches.

Only about half of non-membrane-bound proteins encoded by either bacterial or archaeal genomes are soluble when expressed in Escherichia coli (Yee et al., Proc Natl Acad Sci USA 2002;99:1825-1830; Christendat et al., Prog Biophys Mol Biol 200;73:339-345).

Structure of Escherichia coli ribose-5-phosphate isomerase: a ubiquitous enzyme of the pentose phosphate pathway and the Calvin cycle.

Ribose-5-phosphate isomerase A (RpiA; EC 5.3.1.

Crystal structure of Thermotoga maritima 0065, a member of the IclR transcriptional factor family.

Members of the IclR family of transcription regulators modulate signal-dependent expression of genes involved in carbon metabolism in bacteria and archaea. The Thermotoga maritima TM0065 gene codes for a protein (TM-IclR) that is homologous to the IclR family. We have determined the crystal structure of TM-IclR at 2.

The crystal structure of spermidine synthase with a multisubstrate adduct inhibitor.

Polyamines are essential in all branches of life. Spermidine synthase (putrescine aminopropyltransferase, PAPT) catalyzes the biosynthesis of spermidine, a ubiquitous polyamine. The crystal structure of the PAPT from Thermotoga maritima (TmPAPT) has been solved to 1.