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. Promotes the relocalization of the SNF1 kinase complex to the nucleus upon shift to nonfermentable carbon sources. 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. Interacts with REE1. Resides in the cytosol during growth on fermentable carbon sources and relocalizes rapidly to the nucleus in response to carbon stress. Phosphorylated by SNF1 in vitro. Present with 3590 molecules/cell in log phase SD medium. Belongs to the 5'-AMP-activated protein kinase beta subunit family.