It has been reported recently that the isolated and renatured 23-kDa N-terminal fragment of rabbit skeletal muscle myosin binds tightly to F-actin in an ATP-dependent manner [Muhlrad, A. (1989) Biochemistry 28, 4002-4010]. The binding to actin is of electrostatic nature and may involve a positively charged cluster of residues on the 23-kDa fragment stretching from Arg-143 to Arg-147. An octapeptide containing this positive cluster was synthesized and coupled to BSA through a cysteine residue added to the N-terminus of the peptide. Polyclonal antibody was raised against the BSA-coupled peptide in rabbits which recognized the N-terminal 23-kDa fragment of rabbit skeletal myosin subfragment 1, and a peptide comprised of residues 122-204 of the 23K fragment in Western blots. The purified antibody [IgG and F(ab)] inhibited the actin-activated ATPase activity of S1 without affecting its Mg2(+)- and K+(EDTA)-modulated ATPase activity. Both IgG and F(ab) decreased the binding of S1 to F-actin in a sedimentation assay, and actin inhibited the binding of both IgG and F(ab) to S1 in a competitive binding assay. The cysteine thiol of the synthetic octapeptide was labeled by the fluorescent thiol reagent monobromobimane, and the labeled peptide was found to bind to actin in a sedimentation assay. The results support the possibility that the positively charged Arg-143 to Arg-147 stretch of residues on the 23-kDa fragment participates in actin binding of myosin and may represent an essential constituent of the actin-S1 interface.

Peroxynitrite (OONO-) is closely related to the occurrence and development of health and inflammatory diseases. The physiological and pathological results of OONO- are related to the local concentration of ONOO-. Therefore, to develop of a simple, rapid and reliable OONO- detection tool is badly needed. In this work, we developed a small-molecule near-infrared (NIR) turn-on fluorescence sensor (NN1), harnessing a well-known response group phenylboronic acid response toward OONO-. It shows high detection sensitivity and yields a ratio (I658/I0) fluorescence enhancement (∼280-fold). In addition, NN1 can be effectively used to detect endogenous and exogenous ONOO- in living inflammatory cells. Notably, NN1 can be applied to OONO- imaging analysis in drug-induced inflammatory mice model with satisfactory results. Therefore, NN1 is a robust molecular biological tool, which has a good prospect in the study of ONOO- and the occurrence and development of inflammatory diseases.

The INO80 chromatin remodeling complex plays an essential role in the regulation of gene transcription, which participate in a variety of important biological processes in cells including DNA repair and DNA replication. Difference from the yeast INO80 complex, metazoan INO80 complex have the specific subunit G, which is known as nuclear factor related to kappaB binding protein (NFRKB). Recently, NFRKB has been received much attention in many aspects, such as DNA repair, cell pluripotency, telomere protection, and protein activity regulation. To dig the new function of metazoan INO80 complex, a better understanding of the role of NFRKB is required. In this review, we provide an overview of the structure and function of NFRKB and discuss its potential role in cancer treatment and telomere regulation. Overall, this review provides an important reference for further research of the INO80 complex and NFRKB.

Hydrogen polysulfide (H2Sn, n > 1) is an important active sulfur molecule (RSS) in organisms, which have been considered to be involved in redox signaling and cytoprotective processes. In this work, in order to quickly and accurately detect H2Sn in biosystems, 2-fluoro-5-nitrobenzoic ester was used as the response moiety for H2Sn, and the FRET strategy was adopted to effectively connect the donor (6-hydroxy-2-naphthoic acid) and acceptor (4-substituted-1,8-naphthalimide) to construct a new ratiometric H2Sn fluorescent probe NPNA-H2Sn. NPNA-H2Sn exhibited a more than ∼ 8.0-fold ratio enhancement towards H2Sn at I450/I526 and a very high sensitivity with a very low detection limit of 40.3 nM. Impressive, NPNA-H2Sn was further used for fluorescence imaging of H2Sn in living cells and zebrafish, which showed high-clear ratiometric images. Therefore, we have demonstrated that NPNA-H2Sn could be applied for ratiometric images of endogenous H2Sn in living biosystems and provide a powerful molecular tool for evaluating the physiological and pathological functions of H2Sn.