Is an American allowed to conduct business with Iranian companies from abroad?

Let’s say I’m an American, working for a European company. The European company doesn’t face the same restrictions to trading with Iran (right or wrong) that an American company does. If I handle exports for said European company, does my status as an American citizen mean that I’m subject to the American sanctions against Iran?

As an example, while my colleagues can freely travel to Cuba, I obviously can’t. Is it the same with commercial sanctions?

Caveat: I’m well aware that the government of Iran is, at best, comprised of reactionary assholes. I’m not asking about the morality of anyone involved (US, Iran, EU, etc). I’m just curious whether I ought to stick to my gut feeling and ask a colleague to handle a prospective account in Iran.