No abstract

This study aimed to identify the intracellular binding partner of a unique class of staphylococcal secreted exotoxins called superantigen‐like proteins (SSL) from human macrophage and keratinocyte cell lysates. Here, we report that SSL1 specifically binds to human extracellular signal‐regulated kinase 2 (hERK2), an important stress‐activated kinase in mitogen‐activated protein kinase signaling pathways. Western blot and in vitro binding studies with recombinant hERK2 confirmed the binding interaction of SSL1, SSL7, and SSL10 with hERK2. Moreover, the SSLs‐hERK2 interaction was validated biochemically by ELISA. Our finding shows that SSLs play a novel role by binding with host cell MAP kinase signaling pathway protein. Understanding the SSL‐hERK2 interaction will also provide a basis for designing SSL‐based peptide inhibitors of hERK2 in cancer therapy.

No abstract

The type V-K CRISPR-Cas system, featured by Cas12k effector with a naturally inactivated RuvC domain and associated with Tn7-like transposon for RNA-guided DNA transposition, is a promising tool for precise DNA insertion. To reveal the mechanism underlying target DNA recognition, we determined a cryo-EM structure of Cas12k from cyanobacteria Scytonema hofmanni in complex with a single guide RNA (sgRNA) and a double-stranded target DNA. Coupled with mutagenesis and in vitro DNA transposition assay, our results revealed mechanisms for the recognition of the GGTT PAM sequence and the structural elements of Cas12k critical for RNA-guided DNA transposition. These structural and mechanistic insights should aid in the development of type V-K CRISPR-transposon systems as tools for genome editing.