Figure 5.

Inactivation of Ure2p by using proline as a nitrogen source does not make lug1Δ strains slow growing. Although lug1Δ [URE3] and lug1Δ ure2Δ cells grow poorly on minimal proline glucose plates (or minimal ammonium glucose plates), lug1Δ URE2⁺ cells do not show slow growth on proline, although this condition is well known to inactivate the nitrogen catabolite repression activity of Ure2p (Cooper 2002).