No abstract

Thrombomodulin (TM) is an endothelial anticoagulant cofactor that promotes thrombin-mediated formation of activated protein C (APC). We have found that the N-terminal lectin-like domain (D1) of TM has unique antiinflammatory properties. TM, via D1, binds high-mobility group-B1 DNA-binding protein (HMGB1), a factor closely associated with necrotic cell damage following its release from the nucleus, thereby preventing in vitro leukocyte activation, in vivo UV irradiation-induced cutaneous inflammation, and in vivo lipopolysaccharide-induced lethality. Our data also demonstrate antiinflammatory properties of a peptide spanning D1 of TM and suggest its therapeutic potential. These findings highlight a novel mechanism, i.e., sequestration of mediators, through which an endothelial cofactor, TM, suppresses inflammation quite distinctly from its anticoagulant cofactor activity, thereby preventing the interaction of these mediators with cell surface receptors on effector cells in the vasculature.

One-dimensional (1D) sliding of the tumor suppressor p53 along DNA is an essential dynamics required for its efficient search for the binding sites in the genome. To address how the search process of p53 is affected by the changes in the concentration of Mg(2+) and Ca(2+) after the cell damages, we investigated its sliding dynamics at different concentrations of the divalent cations. The 1D sliding trajectories of p53 along the stretched DNA were measured by using single-molecule fluorescence microscopy. The averaged diffusion coefficient calculated from the mean square displacement of p53 on DNA increased significantly at the higher concentration of Mg(2+) or Ca(2+), indicating that the divalent cations accelerate the sliding likely by weakening the DNA-p53 interaction. In addition, two distributions were identified in the displacement of the observed trajectories of p53, demonstrating the presence of the fast and slow sliding modes having large and small diffusion coefficients, respectively. A coreless mutant of p53, in which the core domain was deleted, showed only a single mode whose diffusion coefficient is about twice that of the fast mode for the full-length p53. Thus, the two modes are likely the result of the tight and loose interactions between the core domain of p53 and DNA. These results demonstrated clearly that the 1D sliding dynamics of p53 is strongly dependent on the concentration of Mg(2+) and Ca(2+), which maintains the search distance of p53 along DNA in cells that lost homeostatic control of the divalent cations.

The need for atom‐precise biomolecule modification, and particularly the irreversible formation of covalent bonds to specific amino acids in proteins, has become an essential issue in the fields of pharmaceuticals and chemical biology. For example, antibody–drug conjugates (ADCs) are increasingly common entries into the clinical oncology pipeline. Herein, we report a new method of affinity peptide mediated regiodivergent functionalization (AJICAP™) that enables the synthesis of ADCs from native IgG antibodies. We succeeded in introducing thiol functional groups onto three lysine residues in IgGs using Fc affinity peptide reagents without antibody engineering. A cytotoxic molecule was then connected to the newly introduced thiol group, and both a surface plasmon resonance binding assay and in vivo xenograft mouse model results showed that the resulting ADC could selectively target and kill HER2‐positive cells. Our strategy provides a new approach for constructing complex antibody‐derived biomolecules.

Lysozymes were purified from three invertebrates: a marine bivalve, a marine conch, and an earthworm. The purified lysozymes all showed a similar molecular weight of 13 kDa on SDS/PAGE. Their N-terminal sequences up to the 33rd residue determined here were apparently homologous among them; in addition, they had a homology with a partial sequence of a starfish lysozyme which had been reported before. The complete sequence of the bivalve lysozyme was determined by peptide mapping and subsequent sequence analysis. This was composed of 123 amino acids including as many as 14 cysteine residues and did not show a clear homology with the known types of lysozymes. However, the homology search of this protein on the protein or nucleic acid database revealed two homologous proteins. One of them was a gene product, CELF22 A3.6 of C. elegans, which was a functionally unknown protein. The other was an isopeptidase of a medicinal leech, named destabilase. Thus, a new type of lysozyme found in at least four species across the three classes of the invertebrates demonstrates a novel class of protein/lysozyme family in invertebrates. The bivalve lysozyme, first characterized here, showed extremely high protein stability and hen lysozyme-like enzymatic features.Keywords: lysozyme; invertebrate; purification; characterization; sequence.Lysozyme is a ubiquitous enzyme that is wildly distributed in the animal kingdom [1]. The biological function of this enzyme is believed to be self-defense from bacterial infection because it induces bacterial cell lysis by hydrolyzing b-1,4 linked glycosidic bond of the peptidoglycan on the bacterial cell wall [2].It is known that several types of lysozymes are distributed in the different parts of the animal kingdom. Goose-type and phage-type lysozymes are found in a part of avian [1] and bacterial phages [3], respectively. Other types of lysozymes are also seen in plants [4] and bacteria [5]. Chicken-type lysozyme is the most conventional one, being distributed in a large number of vertebrates [1] from fish to mammals and also found in insects like moths and flies [6]. Jolles and Jolles purified and partially sequenced another invertebrate lysozyme from a marine invertebrate, a starfish called Asterias rubens [7]. However, its N-terminal sequence was not similar to that of any known type of lysozyme including the chicken type lysozyme, implicating a novel type of lysozyme. Other invertebrate lysozymes had been purified and partially characterized [8±11], but the sequence data were not complete.To investigate the structure and function of invertebrate lysozyme, we purified lysozymes from three species of invertebrates: a marine bivalve, a marine conch, and an earthworm. We determined the N-terminal sequences of the three species and the complete sequence of the marine bivalve lysozyme. The biological function and evolutionary importance of this enzyme were discussed on the basis of the sequence and enzymatic properties. EXPERIMENTAL PROCEDURES Purification of bivalve lysozymeMarine bivalves (Tapes ...