Component of the spindle pole body (SPB) required for insertion of the nascent SPB into the nuclear envelope and for the proper execution of spindle pole body (SPB) duplication. Connects the central plaque of the SPB with the half-bridge. Required for proper localization of CDC5 at the SPB and for proper M-phase progression. Homodimer. Interacts with KAR1, MPS2 and SPC29. Associates with the periphary of the central plaque. The C-ter coiled-coil domain is sufficient for localization and homodimerization. Present with 922 molecules/cell in log phase SD medium. Belongs to the BBP1 family.