Your basic attacks deals 4 bonus damage to minions and monsters.
I have 60 AD, armor pen runes and such, attacked a minion and only do 60 damage. I checked the minion's hp and its -60 from what it was. Same applies to monsters.
© 2014 Riot Games, Inc. All rights reserved. Riot Games, League of Legends and PvP.net are trademarks, services marks, or registered trademarks of Riot Games, Inc.