Centaurin-alpha(1) is a member of the family of ADP-ribosylation factors (ARF) GTPase activating proteins (GAPs), although ARF GAP activity has not yet been demonstrated. The human homologue, centaurin-alpha(1) functionally complements the ARF GAP activity of Gcs1 in yeast. Although Gcs1 is involved in the formation of actin filaments in vivo, the function of centaurin remains elusive. We have identified a number of novel centaurin-alpha(1) binding partners; including CKIalpha and nucleolin. In this report, we have focused on the interaction of centaurin-alpha(1) with PKC. All groups of PKC associate directly through their cysteine rich domains. Centaurin-alpha(1) is also a substrate for all PKC classes and we have identified the two sites of phosphorylation. This is the first report of a kinase that phosphorylates centaurin-alpha(1). (C) 2003 Elsevier Inc. All rights reserved.