We introduce a graph-theoretic model for predicting the supersecondary structure 
of transmembrane β-barrel proteins--a particular class of proteins that performs 
diverse important functions but it is difficult to determine their structure 
with experimental methods. This ab initio model resolves the protein folding 
problem based on pseudo-energy minimization with the aid of a simple 
probabilistic filter. It also allows for determining structures whose barrel 
follows a given permutation on the arrangement of β-strands, and allows for 
rapidly discriminating the transmembrane β-barrels from other kinds of proteins. 
The model is fairly accurate, robust and can be run very efficiently on PC-like 
computers, thus proving useful for genome screening.