As agent autonomy emphasises the need of norms for governing agent interactions, increasing attention is being devoted to (electronic) institutions for modelling organisations governed by norms. Moving from the concepts of role (with its normative consequences, i.e. obligations, permissions and prohibitions), norms (both regulative and constitutive), and normative agents, we first introduce the notion of Computational Institution for modelling norm-regulated MAS. Then, we discuss how infrastructural abstractions like coordination artifacts can be exploited to express norms inside computational institutions, and present an example based on the TuCSoN infrastructure.