TitleThe LC8 Recognition Motif Preferentially Samples Polyproline II Structure in Its Free State.
Publication TypeJournal Article
Year of Publication2017
AuthorsMorgan JL, Jensen MRingkjøbi, Ozenne V, Blackledge M, Barbar E
Date Published2017 09 05
KeywordsAmino Acid Sequence, Binding Sites, Cell Cycle Proteins, Cytoplasmic Dyneins, Microtubule-Associated Proteins, Nuclear Pore Complex Proteins, Protein Conformation, beta-Strand, Saccharomyces cerevisiae Proteins

LC8 is a ubiquitous hub protein that binds intrinsically disordered proteins and promotes their assembly into higher-order complexes. A common feature among the more than 100 essential LC8 binding proteins is that in the 10-12-amino acid recognition sequence there is a conserved QT motif but variable amino acids N- and C-terminal to the QT pair. The sequence diversity among LC8 binding partners implies that structural factors also contribute to specificity. To investigate whether one such factor is the transient secondary structure favored by an LC8 binding sequence, we report here a molecular ensemble description of IC, a domain of the dynein intermediate chain that includes binding sites for light chains LC8 and Tctex1. Nuclear magnetic resonance secondary chemical shifts and residual dipolar coupling values combined with ensemble generation and selection algorithms indicate a deviation from statistical (random) coil behavior with an elevated population of polyproline II (PPII) conformations for the ICregions that bind LC8 and Tctex1. Independent measurements of one- and three-bond scalar couplings confirm the PPII transient secondary structure propensity. Given that in the IC/Tctex1/LC8 ternary complex ICforms a β-strand at the interface of Tctex1 and LC8, we hypothesize that a PPII conformation may facilitate its initial docking and insertion into the binding cleft of the β-sheet LC8 dimer interface. Molecular ensemble calculations for intrinsically disordered LC8 binding partners also reveal PPII conformational sampling within and proximate to the LC8 recognition motifs, suggesting that a preference for a PPII conformation is general for LC8 binding partners.

Alternate JournalBiochemistry
PubMed ID28792212
Grant ListS10 OD018518 / OD / NIH HHS / United States