Structure and Dynamics of Mono- vs. Doubly Lipidated Rab5 in Membranes

• Published in: International journal of molecular sciences Vol. 20; no. 19; p. 4773
• Main Authors: Münzberg, Eileen, Stein, Matthias
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 26.09.2019; MDPI
• Subjects: Amino Acid Sequence; C-Terminus; Carbon; Cell cycle; Cholesterol; Cysteine; Diffusion; Endosomes; gtpase; Guanosine diphosphate; Guanosines; Intracellular Membranes - chemistry; Intracellular Membranes - metabolism; lipid bilayer; Lipids; Localization; Membrane composition; Membrane Lipids - chemistry; Membrane Lipids - metabolism; Membrane proteins; Membranes; Models, Molecular; Molecular Conformation; molecular dynamics; Nucleotides; Post-translation; post-translation modification; Protein Binding; Protein composition; Protein Interaction Domains and Motifs; Proteins; Rab protein; rab5 GTP-Binding Proteins - chemistry; rab5 GTP-Binding Proteins - metabolism; Random walk theory; Residues; Simulation; Structure-Activity Relationship; Vesicle fusion; lipid bilayer; diffusion; post-translation modification; molecular dynamics; GTPase
• ISSN: 1422-0067; 1661-6596; 1422-0067
• DOI: 10.3390/ijms20194773

The Rab5 small GTPase is a regulator of endosomal trafficking and vesicle fusion. It possesses two adjacent cysteine residues for post-translational geranylgeranylation at its C-terminus for the protein to associate with the early endosome membrane. We compare the effect of mono-lipidification of only one cysteine residue with the doubly modified, fully functional Rab protein in both guanosine diphosphate (GDP)- and guanosine triphosphate (GTP)-bound states and in different membranes (one, three, and six-component membranes). Molecular simulations show that the mono-geranylgeranylated protein is less strongly associated with the membranes and diffuses faster than the doubly lipidated protein. The geranylgeranyl anchor membrane insertion depth is smaller and the protein-membrane distance distribution is broad and uncharacteristic for the membrane composition. The mono-geranylgeranylated protein reveals an unspecific association with the membrane and an orientation at the membrane that does not allow a nucleotide-specific recruitment of further effector proteins. This work shows that double-lipidification is critical for Rab5 to perform its physiological function and mono-geranylgeranylation renders it membrane-associated but non-functional.