The effect of an engineered ATCUN motif on the structure and biophysical properties of the SH3 domain of c-Src tyrosine kinase

Fabrication of Nanocatalytic Medicine from Self-Assembling Peptides Containing an ATCUN-Like Copper-Binding Motif for Anticancer Therapy

Development of nanomaterials with multiple enzymatic activities via a facile approach receives growing interests in recent years. Although peptide self-assembling provides an effective approach for the construction of biomimetic materials in recent years, fabrication of artificial enzymes from self-assembling peptides with multiple catalytic activities for anticancer therapy is still a challenge. Here, we report a simple method to prepare nanocatalysts with multienzyme-like activities from self-assembling peptides containing ATCUN copper-binding motifs. With the aid of the coordination interactions between the ATCUN motif and Cu(II) ions, these peptides could perform supramolecular self-assembly to form nanomaterials with biomimetic peroxidase, ascorbate oxidase and glutathione peroxidase activities. Moreover, these trienzyme-like effects can elevate oxidative stress levels and suppress the antioxidative capability of cancer cells, which synergistically induce the apoptosis of cancer cells. Because of the high biocompatibility, catalytic activities and drug encapsulation properties, this self-assembled peptide provides a biomimetic platform for the development of new nanocatalytic medicines for multimodal synergistic cancer therapies.

The impact of oncogenic mutations of the viral Src kinase on the structure and stability of the SH3 domain

Src kinase belongs to the family of Src-related nonreceptor tyrosine kinases. Because of its physiological role in cell growth and proliferation, its activity is strictly controlled by several mechanisms. Nevertheless, in viral Src kinase (v-Src) some of these mechanisms fail, and its uncontrolled activity is responsible for the occurrence of cancer. Here, the crystal structures of three SH3-domain mutants of v-Src were determined to unveil the effects of these oncogenic mutations in this regulatory domain. Mutations in the n-Src and distal loops have a low impact on the overall structure of the domain and its capacity to form intertwined dimers. However, mutations in the RT loop compromise the stability of the domain and make the protein very prone to aggregation. Additionally, these mutations prevent the formation of intertwined dimers. The results show a synergistic effect between mutations in the RT loop and those in the n-Src and distal loops. Analysis of the structures of the v-Src SH3-domain mutants and the closed inactive conformation of cellular Src kinase (c-Src) point to a loss of the interactions that are required to establish the compact inactive form of the kinase. Nevertheless, an analysis of structures of the c-Src SH3 domain complexed with class I and II peptides points to minor changes in the interactions between the v-Src SH3 domain and these peptides. In this way, the structures reported here indicate that mutations in the RT loop might impair the kinase regulation mechanism without affecting the recognition of short proline-rich motifs in the target proteins of the kinase, thus explaining the oncogenic behaviour of the protein.