We report the identification of five proteins expressed specifically on the bacterial magnetic particle (BMP) membrane of Magnetospirillum sp. AMB-1. These proteins are major components of the BMP membrane. The molecular weights were determined to be 12.0, 16.0, 24.8, 35.6, and 66.2 kDa by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Of these five, the 16.0-kDa protein was the most abundant in the BMP membrane. Furthermore, the 16.0-kDa protein consisted of two components each of differing pI. The 35.6-kDa protein was the second most abundant protein of the five detected.