Show simple item record

Residue level characterization of molecular interactions of intermembrane space domains governing the preprotein import into the mitochondrial matrix

dc.contributor.advisorZweckstetter, Markus Prof. Dr.
dc.contributor.authorBajaj, Rakhi
dc.titleResidue level characterization of molecular interactions of intermembrane space domains governing the preprotein import into the mitochondrial matrixde
dc.contributor.refereeRehling, Peter Prof. Dr.
dc.description.abstractengMitochondrial matrix targeting proteins are translated as preproteins (carrying an N-terminal 20-50 residue presequence) in the cytoplasm. Post-translationally, they are imported into the mitochondrial matrix through multi-subunit protein machineries called translocases. The intermembrane space domains (ims) of both the outer and inner mitochondrial membrane translocases perform multiple functions including presequence-receptor binding, translocation contact site constituent and regulation of channel activity across the inner mitochondrial membrane. TIM23 is the translocase of the inner mitochondrial membrane comprising of Tim17, Tim21, Tim23, Tim50 and motor subunits in S.cerevisiae. Here, we have characterized the intermembrane space domains (ims) of Tim23 and Tim21 in solution. We show that Tim21ims is a folded protein and exhibits monomer-dimer equilibrium in solution. The monomeric Tim21ims undergoes dynamics in β-sheet that might play important role in its dimerization. Tim23ims is intrinsically disordered and exists as monomer in solution and is engrossed in a multitude of interactions in the intermembrane space of mitochondria to facilitate import of matrix targeted preproteins. Using solution NMR spectroscopy, the atomic details of binding sites of disordered Tim23 with functionally important ligands (Tim21, Tom22, Tom40, Tim50, mitochondrial membrane mimics and presequence) are elucidated. We have identified five hydrophobic linear motifs in Tim23 involved in binding the aforementioned ligands. We also demonstrate that in disordered Tim23, residues 58-78 acts as hub region and its interactions with aforesaid ligands is regulated by well-placed multivalent hydrophobic motifs, which clearly provide the molecular basis for working of exuberant Tim23 in mitochondria. The role and structural characterization of Tim23ims in two different complexes, one involving membrane mimics (Tim23-DHPC micelles) and another with Tim21, corroborate the lack of regular secondary structure in its bound form. We propose a model for the weak interaction of Tim21-Tim23 intermembrane space domain that describes the binding of short linear hydrophobic motifs of Tim23ims at single site in Tim21ims. Our interaction studies underline the importance of interplay of hydrophobic linear motifs in providing specificity and explicit affinity in interactions involving disordered proteins. This study establishes the need of multiple hydrophobic binding motifs of disordered domains to interact in synergistic manner in transiently weak complex of Tim21-Tim23 and highlights the precise selectivity of hydrophobic motifs as in Tim23-DHPC
dc.contributor.coRefereeTittmann, Kai Prof. Dr.
dc.contributor.thirdRefereeTittmann, Kai Prof. Dr.
dc.subject.gerTIM23 complex interactionsde
dc.subject.gerNMR Mitochondrial Protein importde
dc.subject.engTIM23 complex interactionsde
dc.subject.engNMR Mitochondrial Protein importde
dc.affiliation.instituteGöttinger Graduiertenschule für Neurowissenschaften, Biophysik und molekulare Biowissenschaften (GGNB)de
dc.subject.gokfullBiologie (PPN619462639)de

Files in this item


This item appears in the following Collection(s)

Show simple item record