Abstract Under hydrothermal conditions, in the presence of H2BDC, the self-assembly of CdCl2, H2ip or H2NDC at pH = 7 generated two Cd(II)-containing coordination polymers, Cd6(ip)6(μ-H2O)4·H2O (1) and Cd2(NDC)2(μ-H2O)2 (2) (H2BDC/H2ip/H2NDC = 1,4/1,3/1,2-benzenedicarboxylic acid). The structures are 2D metal-organic frameworks constructed from Cd-O-C rod-shaped SBUs (Secondary Building Units). Crystal samples in the solid state display strong fluorescence at 335 and 343 nm. Keywords: Hydrothermal synthesisMOFsSBUsInorganic–organic rod structure Acknowledgements This work was supported by the National Natural Science Foundation of China under Project (50572040).
The two nucleotide binding domains (NBDs) of ATP binding cassette (ABC) transporters dimerize to form composite nucleotide binding sites (NBSs) each containing Walker A and B motifs from one domain and the ABC "C" signature from the other. In many ABC proteins, the NBSs are thought to be functionally equivalent. However, this is not the case for ABCC proteins, such as MRP1, in which NBS1 containing the Walker A and B motifs from the N-proximal NBD1 typically binds ATP with high affinity but has low hydrolytic activity, while the reverse is true of NBS2. A notable feature of NBD1 of the ABCC proteins is the lack of a catalytic Glu residue following the core Walker B motif. In multidrug resistance protein (MRP) 1, this residue is Asp (D793). Previously, we demonstrated that mutation of D793 to Glu was sufficient to increase ATP hydrolysis at NBS1, but paradoxically, transport activity decreased by 50−70% as a result of tight binding of ADP at the mutated NBS1. Here, we identify two atypical amino acids in NBD1 that contribute to the retention of ADP. We found that conversion of Trp653 to Tyr and/or Pro794 to Ala enhanced transport activity of the D793E mutant and the release of ADP from NBS1. Moreover, introduction of the P794A mutation into wild-type MRP1 increased transport of leukotriene C4 approximately 2-fold. Molecular dynamic simulations revealed that, while the D793E mutation increased hydrolysis of ATP, the presence of the adjacent Pro794, rather than the more typical Ala, decreased flexibility of the region linking Walker B and the D-loop, markedly diminishing the rate of release of Mg2+ and ADP. Overall, these results suggest that the rate of release of ADP by NBD1 in the D793E background may be the rate-limiting step in the transport cycle of MRP1.
Homologous recombination (HR) is an error-free DNA double-strand break (DSB) repair pathway, which safeguards genome integrity and cell viability. Human C-terminal binding protein (CtBP)-interacting protein (CtIP) is a central regulator of the pathway which initiates the DNA end resection in HR. Ubiquitination modification of CtIP is known in some cases to control DNA resection and promote HR. However, it remains unclear how cells restrain CtIP activity in unstressed cells. We show that the ubiquitin E3 ligase PPIL2 is recruited to DNA damage sites through interactions with an HR-related protein ZNF830, implying PPIL2's involvement in DNA repair. We found that PPIL2 interacts with and ubiquitinates CtIP at the K426 site, representing a hereunto unknown ubiquitination site. Ubiquitination of CtIP by PPIL2 suppresses HR and DNA resection. This inhibition of PPIL2 is also modulated by phosphorylation at multiple sites by PLK1, which reduces PPIL2 ubiquitination of CtIP. Our findings reveal new regulatory complexity in CtIP ubiquitination in DSB repair. We propose that the PPIL2-dependent CtIP ubiquitination prevents CtIP from interacting with DNA, thereby inhibiting HR.
Proper cell division at the mid-site of Gram-negative bacteria reflects stringent regulation by the min system (MinC, MinD and MinE). Herein we report crystal structure of the C-terminal domain of MinC from Escherichia coli (EcMinCCTD). The MinCCTD beta helical domain is engaged in a tight homodimer, similar to Thermotoga maritima MinCCTD (TmMinCCTD). However, both EcMinCCTD and TmMinCCTD lack an α-helix (helix3) at their C-terminal tail, in comparison to Aquifex aerolicu MinCCTD (AaMinCCTD) which forms an extra interaction interface with MinD. To understand the role of this extra binding element in MinC/MinD interactions, we fused this helix (Aahelix3) to the C-terminus of EcMinC and examined its effect on cell morphology and cell growth. Our results revealed that Aahelix3 impaired normal cell division in vivo. Furthermore, results of a co-pelleting assay and binding free energy calculation suggested that Aahelix3 plays an essential role in AaMinCD complex formation, under the circumstance of lacking MinE in A. aerolicu. Combining these results with sequence analysis of MinC and MinD in different organisms, we propose an evolutionary relationship to rationalize different mechanisms in cell division positioning in various organisms.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
In this work, we fabricated a high-performance and biocompatible porous triboelectric nanogenerator (TENG) with friction layers made by silk fibroin (SF)@MXene composite aerogel (SF@MXene-A) and a PDMS sponge. The incorporation of MXene into the SF aerogel increases the specific surface area as well as the resulting surface charge density, providing a way for designing a high-performance aerogel TENG. The TENG with the biocompatible SF aerogel achieves an optimum output performance at a ratio of MXene to SF of about 1:1, obtaining a maximum open-circuit voltage (Voc) of 545 V and maximum short-circuit current (Isc) of 16.13 μA. The Voc of our SF@MXene-A based TENG is about 2–3 times larger than the reported best values of other aerogel-based TENGs. In addition, owing to the recognized biocompatibility and advantageous air permeability of the SF@MXene-A, we designed a bioporous TENG mask that diagnoses asthma symptoms. The SF@MXene-A based TENGs have potential applications as wearable devices for diagnosing breath-relevant diseases.
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