Security	Date	Code	Shares	Price	A/D	Owned after	D/I	Nature of ownership
Common Units (Limited Partner Interests)^F1,F2,F3,F4	Sep 1, 2016	D	21,401,137	—	D	58,064,999	I	See Footnotes
Common Units (Limited Partner Interests)^F2,F3,F4,F5	Sep 2, 2016	A	28,554,314	—	A	86,619,313	I	See Footnotes

Table II — derivative securities

No Table II lines on this filing.

Explanation of responses

F1Pursuant to a Master Reorganization Agreement effective September 1, 2016 by and among MPLX Holdings Inc. ("Holdings"), MarkWest Energy Partners, L.P. ("MarkWest"), MWE GP LLC ("MWE GP"), MPLX LP ("MPLX"), MPLX GP LLC ("the "General Partner"), MPC Investment LLC ("MPC Investment"), MPLX Logistics Holdings LLC ("Logistics Holdings") and MarkWest Hydrocarbon, L.L.C. ("Hydrocarbon"), MPLX transferred 980 shares of Holdings common stock to Logistics Holdings in exchange for 21,401,137 common units held by Logistics Holdings.
F2This Form 4 is filed jointly by Marathon Petroleum Corporation ("MPC"), MPC Investment, the General Partner, Logistics Holdings, Holdings and Hydrocarbon. MPC Investment, a direct wholly-owned subsidiary of MPC, owns all of the membership interests or stock in the General Partner, Logistics Holdings and Holdings. Holdings owned all of the membership interests in Hydrocarbon as of September 2, 2016. Accordingly, the General Partner, Logistics Holdings and Holdings are all indirect wholly-owned subsidiaries of MPC, and Hydrocarbon was an indirect wholly-owned subsidiary of MPC as of September 2, 2016.
F3The General Partner directly owns 7,193,467 general partner units, representing a 2% general partner interest in the Issuer. MPC Investment owns all of the membership interests or stock in the General Partner, Logistics Holdings and Holdings and MPC owns all of the membership interests in MPC Investment. Holdings owned all of the membership interests in Hydrocarbon as of September 2, 2016. Accordingly, MPC and MPC Investment both may be deemed to have indirectly beneficially owned the securities of the Issuer directly held by the General Partner, Logistics Holdings, Holdings and Hydrocarbon but disclaim beneficial ownership except to the extent of their respective pecuniary interests therein.
F4The General Partner directly owns 7,193,467 general partner units, representing its 2% general partner interest in the Issuer.
F5Pursuant to a Master Reorganization Agreement effective September 1, 2016 by and among Holdings, MarkWest, MWE GP, MPLX, the General Partner, MPC Investment, Logistics Holdings and Hydrocarbon, all issued and outstanding Class A Units representing limited partner interests of MPLX were exchanged for newly created and issued common units representing limited partner interests of MPLX on a one-to-one conversion, eliminating all issued and outstanding Class A Units representing limited partner interests of MPLX.