Nature 396, 180–183 (1998)

In this letter, we stated that the isoform of p21-activated protein kinase (PAK) purified from rat spleen was Pak3. At the time of going to press, this was correct nomenclature for the rat isoform based on the SwissProt protein sequence database. However, under the restructuring of PAK nomenclature within this database (December 1998) the isoform we had previously purified has now been classified as Pak2. Although we were able to detect phosphorylation of the catalytic domain of Raf-1 (CR3) by the purified kinase, now identified as Pak2, we now note that experiments using recombinant protein (Fig. 3c, d) or DNA constructs (Fig. 4) all used bona fide Pak3 (murine) from a qualified source (R. Cerione laboratory). This suggests the potential involvement of various Pak isoforms in the regulation of Raf-1 activity through phosphorylation of Ser 338.