  A small fraction of all protein structures characterized so far are
entangled. The challenge of understanding the properties of these knotted
proteins, and the why and the how of their natural folding process, has been
taken up in the past decade with different approaches, such as structural
characterization, in vitro experiments, and simulations of protein models with
varying levels of complexity. The simplest among these are the lattice G\=o
models, which belong to the class of structure-based models, i.e., models that
are biased to the native structure by explicitly including structural data. In
this review we highlight the contributions to the field made in the scope of
lattice G\=o models, putting them into perspective in the context of the main
experimental and theoretical results and of other, more realistic,
computational approaches.
