Multicoil2: predicting coiled coils and their oligomerization states from sequence in the twilight zone.

The alpha-helical coiled coil can adopt a variety of topologies, among the most common of which are parallel and antiparallel dimers and trimers. We present Multicoil2, an algorithm that predicts both the location and oligomerization state (two versus three helices) of coiled coils in protein sequences. Multicoil2 combines the pairwise correlations of the previous Multicoil method with the flexibility of Hidden Markov Models (HMMs) in a Markov Random Field (MRF).

Predicting helix orientation for coiled-coil dimers.

The alpha-helical coiled coil is a structurally simple protein oligomerization or interaction motif consisting of two or more alpha helices twisted into a supercoiled bundle. Coiled coils can differ in their stoichiometry, helix orientation, and axial alignment. Because of the near degeneracy of many of these variants, coiled coils pose a challenge to fold recognition methods for structure prediction.

Anticipatory active-site motions and chromophore distortion prime photoreceptor PYP for light activation.

Protein photoreceptors use small-molecule cofactors called chromophores to detect light. Only under the influence of the receptors' active sites do these chromophores adopt spectral and photochemical properties that suit the receptors' functional requirements. This protein-induced change in chromophore properties is called photochemical tuning and is a prime example for the general--but poorly understood--process of chemical tuning through which proteins shape the reactivity of their active-site groups.