SAMHD1 and HIV-1 infection: Interestingly, the LF620AA substitution in the C terminus resulted in an increased rate of dNTP hydrolysis by as much as 50%, as did a deletion of the N-terminal region including the SAM domain (Fig. 2C), suggesting that these latter elements can modulate SAMHD1 catalytic activity, consistent with our finding that these same mutations enhance HIV-1 infection inhibition by HIV-1.