One year after taking over Gillette, Procter & Gamble Co. this week cut 300 Gillette jobs, as part of its estimated 5,000 job cuts expected as a result of the takeover. P&G had already eliminated about 2,800 positions, with more than half coming from Gillette. Gillette’s former corporate headquarters in Boston, at the Prudential tower, has seen half of its 1,000 employees either leave the company or transfer to other Procter operations in other cities. Workers have for months know about the job losses, according to Procter. Procter purchased Gillette for $54 million last October.