AMP-activated protein kinase β-subunit requires internal motion for optimal carbohydrate binding

Abstract

AMP-activated protein kinase interacts with oligosaccharides and glycogen through the carbohydrate-binding module (CBM) containing the β-subunit, for which there are two isoforms (β 1 and β 2). Muscle-specific β 2-CBM, either as an isolated domain or in the intact enzyme, binds carbohydrates more tightly than the ubiquitous β 1-CBM. Although residues that contact carbohydrate are strictly conserved, an additional threonine in a loop of β 2-CBM is concurrent with an increase in flexibility in β 2-CBM, which may account for the affinity differences between the two isoforms. In contrast to β 1-CBM, unbound β 2-CBM showed microsecond-to-millisecond motion at the base of a β-hairpin that contains..