CALGARY — Activist shareholders say they’re withholding support for three of TransAlta Corp.’s directors at the upcoming annual meeting to protest a $750-million deal between the utility company and Brookfield Renewable Partners.The protest is led by Mangrove Partners of New York City and Bluescape Energy Partners of Dallas, which collectively control about 10 per cent of TransAlta’s shares.They say they’ll withhold their votes for Gordon Giffin, Alan Fohrer and Beverlee Park at an upcoming meeting and may put forward previously announced alternative nominees.The Ontario Securities Commission will hold a hearing Friday to consider their application to delay the shareholder meeting and require a vote on the Brookfield transaction.Brookfield Renewable Partners and its institutional partners have signed deal to invest a $750-million in TransAlta’s hydro assets. Brookfield will also purchase shares to increase its stake in TransAlta to nine per cent.The U.S. investors say the deal was “rushed” and prevents TransAlta from looking at potential better options.Companies in this story: (TSX:TA, TSX:BEP.UN) read more