June 24 (Reuters) - Abu Dhabi state investor Mubadala has sold around 4.5% of Oil Search Ltd for A$362.8 million ($274.82 million), the Papua New Guinea-based company said in a filing late on Thursday. $1 = 1.3201 Australian dollars Reporting by Nikhil Kurian Nainan in Bengaluru; Editing by Shounak Dasgupta Our Standards: The Thomson Reuters Trust Principles.