B737-900
Inflight Event / Encounter Loss Of Aircraft Control; Inflight Event / Encounter Wake Vortex Encounter
Flight Crew Regained Aircraft Control
Environment - Non Weather Related
On left base to final on visual approach for [Runway] 16R; at 4;200 FT; clean configuration; approaching min maneuver speed; hand flying. Encountered wake turbulence from preceding B747 who was on approach to [Runway] 16L. We had this aircraft in sight. Bank angle went abruptly to approximately 45 degrees before I recovered by adding power; unloading and rolling wings level. Subsequently intercepted final and got on glideslope for a stable approach by 1;000 FT and made an uneventful landing. Made PA after landing to inform passengers and flight attendants what we had encountered. Stood at doorway for all deplaning passengers and answered any questions they had about this event.
B737-900 Captain reported wake turbulence from a B747 on approach to SEA on a parallel runway that resulted in a 45 degree bank.