Williams Cos. Inc. (NYSE: WMB) completed a previously announced acquisition of the 50% general partner interest and 55.1 million limited partner units in Access Midstream Partners LP (NYSE:ACMP) for $5.995 billion.

The interest and units were previously held by Global Infrastructure Partners II. Williams now owns 100% of the general partner and about 50% of the limited partner units in Access Midstream Partners.

Williams is proposing the also previously announced merger of Williams Partners LP with and into Access Midstream Partners LP, in a unit-for-unit exchange at a ratio of 0.85 Access Midstream Partners units per Williams Partners unit. The proposal includes an option for Williams Partners unitholders to take either a one-time special payment of 81 cents per unit, or an equivalent value of additional common units of Access Midstream Partners as compensation for a lower expected per-unit limited partner cash distribution in 2015.

If the merger is completed in 2014, the merged MLP is expected to have a 2015 distribution increase of at least 25% above Access Midstream Partners’ current $2.79 per unit. The MLP is also expected to have a best-in-class distribution growth rate of 10% to 12% annually through 2017, strong coverage and strong investment-grade ratings. The merged MLPs would be known as Williams Partners LP and would have an expected 2015 adjusted EBITDA of about $5 billion.