This is what Jim Harbaugh does. He adds quarterbacks.
The 49ers first cut Johnson, who played for Harbaugh at the University of San Diego, during the 2012 preseason. Blaine Gabbert, acquired in a trade in March, is still the favorite to be the backup quarterback to Colin Kaepernick.
To make room for Johnson, the 49ers cut defensive lineman Christian Tupou.
In other 49ers notes:
The signing bonus for the four-year deal signed by fifth-round pick Aaron Lynch, a linebacker, is $198,000.
The 49ers signed fifth-round pick, cornerback Keith Reaser. He is coming off a torn ACL and may not play this season. The 49ers have signed three of their 12 draft picks.