New insights into the structure and function of the complex between the Escherichia coli Hsp70, DnaK, and its nucleotide-exchange factor, GrpE.

The 70 kDa heat shock proteins (Hsp70s) play a pivotal role in many cellular functions using allosteric communication between their nucleotide-binding domain (NBD) and substrate-binding domain, mediated by an interdomain linker, to modulate their affinity for protein clients. Critical to modulation of the Hsp70 allosteric cycle, nucleotide-exchange factors (NEFs) act by a conserved mechanism involving binding to the ADP-bound NBD and opening of the nucleotide-binding cleft to accelerate the release of ADP and binding of ATP. The crystal structure of the complex between the NBD of the Escherichia coli Hsp70, DnaK, and its NEF, GrpE, was reported previously, but the GrpE in the complex carried a point mutation (G122D).

Backbone and ILV side-chain NMR resonance assignments of the catalytic domain of human deubiquitinating enzyme USP7.

Ubiquitin specific protease 7 (USP7) is a deubiquitinating enzyme, which removes ubiquitin tag from numerous protein substrates involved in diverse cellular processes such as cell cycle regulation, apoptosis and DNA damage response. USP7 affects stability, interaction network and cellular localization of its cellular and viral substrates by controlling their ubiquitination status. The large 41 kDa catalytic domain of USP7 harbors the active site of the enzyme.

Selective promiscuity in the binding of Hsp70 to an unfolded protein.

Heat shock protein 70 (Hsp70) chaperones bind many different sequences and discriminate between incompletely folded and folded clients. Most research into the origins of this "selective promiscuity" has relied on short peptides as substrates to dissect the binding, but much less is known about how Hsp70s bind full-length client proteins. Here, we connect detailed structural analyses of complexes between the Hsp70 (DnaK) substrate-binding domain (SBD) and peptides encompassing five potential binding sites in the precursor to alkaline phosphatase (proPhoA) with SBD binding to full-length unfolded proPhoA.

Hsp70 molecular chaperones: multifunctional allosteric holding and unfolding machines.

The Hsp70 family of chaperones works with its co-chaperones, the nucleotide exchange factors and J-domain proteins, to facilitate a multitude of cellular functions. Central players in protein homeostasis, these jacks-of-many-trades are utilized in a variety of ways because of their ability to bind with selective promiscuity to regions of their client proteins that are exposed when the client is unfolded, either fully or partially, or visits a conformational state that exposes the binding region in a regulated manner. The key to Hsp70 functions is that their substrate binding is transient and allosterically cycles in a nucleotide-dependent fashion between high- and low-affinity states.

USP7: Structure, substrate specificity, and inhibition.

Turnover of cellular proteins is regulated by Ubiquitin Proteasome System (UPS). Components of this pathway, including the proteasome, ubiquitinating enzymes and deubiquitinating enzymes, are highly specialized and tightly regulated. In this mini-review we focus on the de-ubiquitinating enzyme USP7, and summarize latest advances in understanding its structure, substrate specificity and relevance to human cancers.

USP7-Specific Inhibitors Target and Modify the Enzyme's Active Site via Distinct Chemical Mechanisms.

USP7 is a deubiquitinating enzyme that plays a pivotal role in multiple oncogenic pathways and therefore is a desirable target for new anti-cancer therapies. However, the lack of structural information about the USP7-inhibitor interactions has been a critical gap in the development of potent inhibitors. USP7 is unique among USPs in that its active site is catalytically incompetent, and is postulated to rearrange into a productive conformation only upon binding to ubiquitin.

PHD domain from human SHPRH.

SHPRH (NF2, istone linker, HD, ING, elicase) is a SWI2/SNF2-family ATP-dependent chromatin remodeling factor, and one of E3 ubiquitin ligases responsible for Ubc13-Mms2-dependent K63 poly-ubiquitination of PCNA (roliferating ell uclear ntigen) that promotes error-free DNA damage tolerance in eukaryotes. In contrast to its functional homologues, Rad5 and human HLTF (elicase ike ranscription actor), SHPRH contains a PHD (lant omeoomain) finger embedded in the ‘minor’ insert region of the core helicase-like domain. PHD fingers are often found in proteins involved in chromatin remodeling and transcription regulation, and are generally considered as ‘readers’ of methylation state of histone tails, primarily the lysine 4 (K4) residue of histone H3 (H3K4).

NMR structure and dynamics of the C-terminal domain from human Rev1 and its complex with Rev1 interacting region of DNA polymerase η.

Rev1 is a translesion synthesis (TLS) DNA polymerase essential for DNA damage tolerance in eukaryotes. In the process of TLS stalled high-fidelity replicative DNA polymerases are temporarily replaced by specialized TLS enzymes that can bypass sites of DNA damage (lesions), thus allowing replication to continue or postreplicational gaps to be filled. Despite its limited catalytic activity, human Rev1 plays a key role in TLS by serving as a scaffold that provides an access of Y-family TLS polymerases polη, ι, and κ to their cognate DNA lesions and facilitates their subsequent exchange to polζ that extends the distorted DNA primer-template.