Energy Secretary Rick Perry informed President Trump on Thursday that he is resigning, Bloomberg first reported and Trump later confirmed. Perry's exact departure date is unknown, but Trump told reporters it would be "at the end of the year" and that he has already picked a successor.

Why it matters: While Perry has largely avoided the kind of controversies that have plagued Trump Cabinet officials like Scott Pruitt and Ryan Zinke, he has recently found himself embroiled in the Ukraine scandal currently at the heart of the House's impeachment inquiry. Perry told the Wall Street Journal on Wednesday that he was directed by President Trump to seek out Rudy Giuliani to discuss the president's concerns about alleged Ukrainian corruption.

The House Intelligence, Foreign Affairs and Oversight committees have subpoenaed Perry to turn over documents by this Friday as part of their investigation into Trump's alleged efforts to push Ukraine to investigate 2020 candidate Joe Biden.

State Department official George Kent told House investigators on Wednesday that the White House removed the core of its Ukraine policy team in the spring and replaced it with "three amigos" — Perry, Ambassador to the EU Gordon Sondland and special envoy to Ukraine Kurt Volker — who were viewed as more open to pressuring Ukraine.

The big picture: Per Axios' Amy Harder, the actual functions of the Energy Department are unlikely to change much after Perry’s exit. Deputy Secretary Dan Brouillette will likely be acting secretary for the time being. Brouillette has a lower profile than Perry but supports the same basic agenda, including nuclear power and exports of liquefied natural gas.

Up until his involvement in the Ukraine saga, Perry had been one of the most non-controversial Cabinet members, even while unabashedly and loudly supporting American gas exports into other nations.

Go deeper: Trump pins Ukraine call on Energy Secretary Rick Perry