Haemophilus influenzae periplasmic protein which binds deoxyribonucleic acid: properties and possible participation in genetic transformation.

A protein which binds to either single-stranded or double-stranded deoxyribonucleic acid (DNA) but not to ribonucleic acid has been isolated by osmotic shock treatment of growing cells. This periplasmic protein differs from the principal intracellular binding protein in its greater thermolability and by the absence of salt-induced cooperativity in its interaction with single-stranded DNA. Certain mutant strains of Haemophilus influenzae defective in the DNA suptake steps of genetic transformation were found to be deficient in periplasmic DNA-binding protein, suggesting that this protein participates in the uptake of DNA in transformation.