MSc Thesis Presentation: Identifying the sugars and phospholipids tightly bound to an integral membrane protein

MSc Candidate

Jeffrey de Vlugt

Abstract

Anabaena Sensory Rhodopsin (ASR) is a microbial photosensor found in cyanobacterium Anabaena sp. PCC 7120. It was found in previous studies that ASR co-purifies with several small molecules, although the identities and structural or functional roles remained unclear. In this thesis, two-dimensional and three-dimensional solid-state nuclear magnetic resonance (NMR) experiments and complementary methods were used to assign NMR signals of these molecules. The identified chemical shift patterns correspond to N-acetyl-D-glucosamine, N-acetyl-D-mannosaminuronic acid, 4-acetomido-4,6-dideoxy-D-galactose, and to a common phospholipid phosphatidylethanolamine (PE). The acyl tails of PE were identified based on characteristic product ion masses using liquid chromatography-mass spectrometry. Numerous correlations atypical for protein amino acids were found in the NMR spectra; they may result from PE acyl tails that are tightly bound by non-covalent interactions along the surface of transmembrane alpha-helices. The sugars likely feature a phospholipid aglycone that allows them to bind to ASR in a similar manner.

Examination Committee

• Dr. Eric Poisson, Chair
• Dr. Vladimir Ladizhansky, Advisor
• Dr. Steffen Graether
• Dr. George Harauz