Abstract
In bacteria, there are a set of lipoproteins that are modified with lipid at their N-terminal cysteine residues. We have already identified two lipoproteins, PsbQ and Psb27, in Synechocystis sp. PCC6803. However, the structure of lipid modification of these lipoproteins has not been determined in detail. In this study, we have analyzed the structure of lipid modification of the lipoproteins using mass spectrometry. As a result, it was found that PsbQ was modified with a diacylglycerol and an acyl group at its N-terminal cysteine residue. Psb27 was also modified with a diacylglycerol but not with acyl group. To investigate the roles of N-acylation, we created a mutant defective in N-acylation of lipoproteins. The mutant showed growth retardation in a calcium-depleted medium and a different sensitivity to several sugars compared to the wild type. These findings indicate that N-acylation of lipoproteins plays important roles in Synechocystis sp. PCC6803.
