CRISPR from Prevotella and Francisella 1 (Cpf1) is an effector endonuclease of the class 2 CRISPR-Cas (clustered regularly interspaced short palindromic repeats-CRISPR-associated proteins) gene editing system. We developed a method for evaluating Cpf1 activity, based on target sequence composition in mammalian cells, in a high-throughput manner. A library of >11,000 target sequence and guide RNA pairs was delivered into human cells using lentiviral vectors. Subsequent delivery of Cpf1 into this cell library induced insertions and deletions (indels) at the integrated synthetic target sequences, which allowed en masse evaluation of Cpf1 activity by using deep sequencing. With this approach, we determined protospacer-adjacent motif sequences of two Cpf1 nucleases, one from Acidaminococcus sp. BV3L6 (hereafter referred to as AsCpf1) and the other from Lachnospiraceae bacterium ND2006 (hereafter referred to as LbCpf1). We also defined target-sequence-dependent activity profiles of AsCpf1, which enabled the development of a web tool that predicts the indel frequencies for given target sequences (http://big.hanyang.ac.kr/cindel). Both the Cpf1 characterization profile and the in vivo high-throughput evaluation method will greatly facilitate Cpf1-based genome editing.

The structure of auxin-binding protein 1 (ABP1) from maize has been determined at 1.9 A Ê resolution, revealing its auxin-binding site. The structure con®rms that ABP1 belongs to the ancient and functionally diverse germin/seed storage 7S protein superfamily. The binding pocket of ABP1 is predominantly hydrophobic with a metal ion deep inside the pocket coordinated by three histidines and a glutamate. Auxin binds within this pocket, with its carboxylate binding the zinc and its aromatic ring binding hydrophobic residues including Trp151. There is a single disul®de between Cys2 and Cys155. No conformational rearrangement of ABP1 was observed when auxin bound to the protein in the crystal, but examination of the structure reveals a possible mechanism of signal transduction.

The crystal structure of Pseudomonas cellulosa mannanase 26A has been solved by multiple isomorphous replacement and refined at 1.85 Å resolution to an R-factor of 0.182 (R-free ‫؍‬ 0.211). The enzyme comprises (␤/␣) 8 -barrel architecture with two catalytic glutamates at the ends of ␤-strands 4 and 7 in precisely the same location as the corresponding glutamates in other 4/7-superfamily glycoside hydrolase enzymes (clan GH-A glycoside hydrolases). The family 26 glycoside hydrolases are therefore members of clan GH-A. Functional analyses of mannanase 26A, informed by the crystal structure of the enzyme, provided important insights into the role of residues close to the catalytic glutamates. These data showed that Trp-360 played a critical role in binding substrate at the ؊1 subsite, whereas Tyr-285 was important to the function of the nucleophile catalyst. His-211 in mannanase 26A does not have the same function as the equivalent asparagine in the other GH-A enzymes. The data also suggest that Trp-217 and Trp-162 are important for the activity of mannanase 26A against mannooligosaccharides but are less important for activity against polysaccharides.

CAD/DFF40 is responsible for the degradation of chromosomal DNA into nucleosomal fragments and subsequent chromatin condensation during apoptosis. It exists as an inactive complex with its inhibitor ICAD/DFF45 in proliferating cells but becomes activated upon cleavage of ICAD/DFF45 into three domains by caspases in dying cells. The molecular mechanism underlying the control and activation of CAD/DFF40 was unknown. Here, the crystal structure of activated CAD/DFF40 reveals that it is a pair of molecular scissors with a deep active-site crevice that appears ideal for distinguishing internucleosomal DNA from nucleosomal DNA. Ensuing studies show that ICAD/DFF45 sequesters the nonfunctional CAD/DFF40 monomer and is also able to disassemble the functional CAD/DFF40 dimer. This capacity requires the involvement of the middle domain of ICAD/DFF45, which by itself cannot remain bound to CAD/DFF40 due to low binding affinity for the enzyme. Thus, the consequence of the caspase-cleavage of ICAD/DFF45 is a self-assembly of CAD/DFF40 into the active dimer.

Oxalate oxidase (EC 1.2.3.4) catalyzes the conversion of oxalate and dioxygen to hydrogen peroxide and carbon dioxide. In this study, glycolate was used as a structural analogue of oxalate to investigate substrate binding in the crystalline enzyme. The observed monodentate binding of glycolate to the active site manganese ion of oxalate oxidase is consistent with a mechanism involving C-C bond cleavage driven by superoxide anion attack on a monodentate coordinated substrate. In this mechanism, the metal serves two functions: to organize the substrates (oxalate and dioxygen) and to transiently reduce dioxygen. The observed structure further implies important roles for specific active site residues (two asparagines and one glutamine) in correctly orientating the substrates and reaction intermediates for catalysis. Combined spectroscopic, biochemical, and structural analyses of mutants confirms the importance of the asparagine residues in organizing a functional active site complex.Oxalate oxidase (OXO; EC 1.2.3.4) 6 catalyzes the oxidation of oxalate, reducing dioxygen to hydrogen peroxide and forming 2 mol of carbonOxalate oxidase is widespread in nature and has been found in bacteria (4), fungi (1, 5), and various plant tissues (6). It has been detected in barley seedling roots during germination and in the leaves of mature barley plants in response to powdery mildew infection (6, 7), suggesting a role in plant signaling and defense. The enzyme has been purified to homogeneity from barley seedling roots and its N-terminal sequence determined, allowing the corresponding cDNA to be isolated and the complete primary sequence to be determined (3,8). These developments led to the recognition that the enzyme, OXO, is identical to an important marker of grain development during germination of wheat called germin (3,8). OXO is a member of a functionally diverse protein superfamily known as the cupins (9) or double stranded ␤-helix proteins (10). Barley OXO forms a hexamer that has extreme stability to heat and proteolysis (11).Spectroscopic studies demonstrated that OXO requires manganese for catalysis (12) and subsequent crystallographic studies on the barley enzyme revealed the structure of the hexamer (Fig. 1a) and confirmed the presence of a mononuclear manganese center buried deep within its jellyroll ␤-barrel domain (13). The manganese is bound by the side chains of three histidines and one glutamate residue, as well as two water molecules that occupy adjacent positions in the roughly octahedral metal complex (Fig. 1b). Based on the lack of obvious optical absorption and the presence of a characteristic EPR spectrum, the manganese ion has been assigned as the reduced Mn(II) oxidation state in the resting enzyme (12). Spectroscopic studies using recombinant OXO expressed in Pichia pastoris confirmed the presence of Mn(II) in the resting recombinant enzyme and provided the first spectroscopic evidence for oxalate binding to the manganese (14). The EPR signal of the anaerobic substrate complex, like that of the nativ...