Brush border myosin I (BBMI) was first identified as a major constituent of the microvillus cytoskeleton, where it links the actin filaments of the microvillus core to the overlying plasma membrane. Recently, however, BBMI was also found on isolated Golgi membranes. This observation suggests that cytoplasmic BBMI might act as a molecular motor for apically targeted secretory vesicles.

In an earlier study from this laboratory a 105-110 kD protein was isolated from the chicken small intestine, which displayed several characteristics of the BBMI. Using an antibody against this BBMI- like protein (MLP), the protein was detected in the apical brush border of the enterocytes. The limited resolution of the light microscopic immunohistochemical techniques used in that investigation, however, did not provide information about the intracellular distribution of MLP in the enterocytes.

In this study the intracellular localization of MLP was characterized using post-embedding colloidal gold immunocytochemistry. Pieces of the jejunum from 6-week-old male White Leghorn chickens were fixed and embedded in LR Gold resin.