Sans looks alot like Swiss 924 from Bitstream - Bitstreams version of Hanseatic

Serif looks like Arena from Berthold

Serif looks like Arena from Berthold

The sans serif is custom, derived from the new logotype for Gagosian designed by abc-xyz and Graphic Thought Facility:
http://www.abc-xyz.co.uk/view/gagosian

It may indeed be custom K. C. but it sure looks a lot like Swiss 924

Not disputing the resemblance to Swiss 924 / Hanseatic/ Information Bold Condensed, just reporting what the designer claims.

The Gagosian face has a shorter crossbar on the E and differs from Swiss 924 in a few other details, but certainly owes a debt to it....

I tried in the font identification website http://en.likefont.com and there are 2956 matched fonts in total, and the most similar font is Information BQ Bold.
This is my identification result page for your image: http://en.likefont.com/community/6346372/