Beta subunit of the SNF1 kinase complex, which is required for transcriptional, metabolic, and developmental adaptations in response to glucose limitation. Has a structural role, mediating heterotrimer formation, and a regulatory role, defining carbon source-regulated subcellular location and substrate specificity of the SNF1 kinase complex. Involved in the regulation of aging. Acts as a negative regulator of nuclear SNF1 activity in young cells by sequestering its activating gamma subunit at the plasma membrane. Component of the SNF1 kinase complex, a heterotrimeric complex composed of the catalytic alpha subunit SNF1, one of the three related beta subunits SIP1, SIP2 or GAL83, and the regulatory gamma subunit SNF4. The beta subunit serves as a bridge between the catalytic and the regulatory subunit. Interacts (via KIS domain) with SNF1. Interacts (via ASC domain) with SNF4. Resides in the cytosol during growth in glucose. Excluded from the nucleus. There is an age-associated shift in localization from the plasma membrane to the cytoplasm. Induced upon shift to nonfermentable carbon sources. Phosphorylated by SNF1 in vitro. Present with 300 molecules/cell in log phase SD medium. Belongs to the 5'-AMP-activated protein kinase beta subunit family.