IscB Nuclease

Product Introduction

IscB (insertion sequences Cas9-like OrfB) is an RNA-guided DNA nuclease encoded within the IS200/IS605 transposon family and is considered an evolutionary ancestor of the CRISPR-Cas9 system. This protein belongs to the OMEGA (Obligate Mobile Element-Guided Activity) system family, and its discovery provides crucial insights into the molecular evolution of CRISPR-Cas systems.

The IscB protein consists of only approximately 400 amino acids, with a molecular weight significantly smaller than typical Cas9 proteins (1000-1400 aa), primarily due to the absence of the α-helical recognition lobe (REC lobe) responsible for recognition functions in Cas9. Despite its small size, IscB retains core nuclease domains similar to Cas9, including RuvC and HNH domains, which are responsible for cleaving the two strands of the DNA duplex. Additionally, IscB contains an N-terminal PLMP domain and a C-terminal TAM-interacting domain (TID).