Histone ubiquitination affects the
structure and function of nucleosomes
through tightly regulated dynamic reversible processes. The efficient
preparation of ubiquitinated histones and their analogs is important
for biochemical and biophysical studies on histone ubiquitination.
Here, we report the CAACU (cysteine-aminoethylation assisted chemical
ubiquitination) strategy for the efficient synthesis of ubiquitinated
histone analogs. The key step in the CAACU strategy is the installation
of an N-alkylated 2-bromoethylamine derivative into a recombinant
histone through cysteine aminoethylation, followed by native chemical
ligation assisted by Seitz’s auxiliary to produce mono- and
diubiquitin (Ub) and small ubiquitin-like modifier (SUMO) modified
histone analogs. This approach enables the rapid production of modified
histones from recombinant proteins at about 1.5–6 mg/L expression.
The thioether-containing isopeptide bonds in the products are chemically
stable and bear only one atomic substitution in the structure, compared
to their native counterparts. The ubiquitinated histone analogs prepared
by CAACU can be readily reconstituted into nucleosomes and selectively
recognized by relevant interacting proteins. The thioether-containing
isopeptide bonds can also be recognized and hydrolyzed by deubiquitinases
(DUBs). Cryo-electron microscopy (cryo-EM) of the nucleosome containing
H2BKC34Ub indicated that the obtained CAACU histones were
of good quality for structural studies. Collectively, this work exemplifies
the utility of the CAACU strategy for the simple and efficient production
of homogeneous ubiquitinated and SUMOylated histones for biochemical
and biophysical studies.
In recent years, the big data emerged as a hot topic because of the rapid growth of the information and wireless communication technology. One of the significant sources of the big data is wireless sensor networks. Due to the power limitation of sensor nodes, energy-efficient big data collecting is a challenging task in wireless sensor networks. Being considered as an effective solution to address this challenge is to utilize sink's mobility to assist data collecting. Although this method can reduce the volume of data transfer between sensor nodes and thus save energy consumption of nodes, the low speed of mobile sink hinders its use in data-intensive sensing applications with time constraint. In this article, we propose a four-phase mobility-assisted data collecting protocol consisting of network clustering, routes planning, routes combination, and data collecting. Two heuristic routes planning algorithms are presented to build a set of trajectories which satisfy the deadline constraint and have the minimum overall movement cost. Numeric results show that our approaches have better performance in terms of energy saving, latency, and movement cost.
Non-reducible disulfide bond replacement was used to study the disculfide exchange between hepcidin and ferroportin, and the results indicate that the hepcidin–ferroportin interaction does not require disfulfide exchange.
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