6OBJ

Structure of a DNA-bound dimer extracted from filamentous SgrAI endonuclease in its activated form

Summary for 6OBJ

• Entry DOI: 10.2210/pdb6obj/pdb
• EMDB information: 20015
• Descriptor: SgraIR restriction enzyme, DNA (26-MER), MAGNESIUM ION (3 entities in total)
• Functional Keywords: restriction endonuclease, dnase, allostery, bacterial innate immunity, filament, hyper-activation, substrate specificity, hydrolase-dna complex, hydrolase/dna
• Biological source: Streptomyces griseus; More
• Total number of polymer chains: 4
• Total formula weight: 100824.59

Authors

Polley, S.,Lyumkis, D.,Horton, N.C. (deposition date: 2019-03-20, release date: 2020-02-26, Last modification date: 2024-03-20)

Primary citation

Polley, S.,Lyumkis, D.,Horton, N.C.
Mechanism of Filamentation-Induced Allosteric Activation of the SgrAI Endonuclease.
Structure, 27:1497-1507.e3, 2019

PubMed Abstract: Filament formation by enzymes is increasingly recognized as an important phenomenon with potentially unique regulatory properties and biological roles. SgrAI is an allosterically regulated type II restriction endonuclease that forms filaments with enhanced DNA cleavage activity and altered sequence specificity. Here, we present the cryoelectron microscopy (cryo-EM) structure of the filament of SgrAI in its activated configuration. The structural data illuminate the mechanistic origin of hyperaccelerated DNA cleavage activity and suggests how indirect DNA sequence readout within filamentous SgrAI may enable recognition of substantially more nucleotide sequences than its low-activity form, thereby altering and partially relaxing its DNA sequence specificity. Together, substrate DNA binding, indirect readout, and filamentation simultaneously enhance SgrAI's catalytic activity and modulate substrate preference. This unusual enzyme mechanism may have evolved to perform the specialized functions of bacterial innate immunity in rapid defense against invading phage DNA without causing damage to the host DNA.

PubMed: 31447289
DOI: 10.1016/j.str.2019.08.001

Experimental method

ELECTRON MICROSCOPY (3.5 Å)