Biochemistry. In the article “Identification by mass spectrometry of the phosphorylated residue responsible for activation of the catalytic domain of myosin I heavy chain kinase, a member of the PAK/STE20 family” by Joanna Szczepanowska, Xiaolong Zhang, Christopher J. Herring, Jun Qin, Edward D. Korn, and Hanna Brzeska, which appeared in number 16, August 5, 1997, of Proc. Natl. Acad. Sci. USA (94, 8503–8508), the authors wish to note that in Fig. 3, the ions of m/z 1345.3 and 1247.1 were incorrectly identified as b13 and b13Δ, respectively, produced by cleavage of the peptide AS(Pi)VVGTTYWMAPEVVK between E and V (Fig. 3 Inset). In fact, these ions are b12 and b12Δ, produced by cleavage of the peptide between P and E. This correction has no effect on the conclusion that the phosphorylated residue is serine. Also, in Table 2, reference numbers 22–24 should be 21–23 (the reference in the legend is cited correctly) and the MIHCK sequence is from residue 624 to residue 638.
Table 2.
Important serine and threonine residues in the linker region of PAK/STE20 kinases
| Enzyme | Sequence | Ref. |
|---|---|---|
| MIHCK | 624KRASVVGTTYWMAPE638 | This paper |
| S6/H4 | 383SSMVGTPYWMAPE395 | 21 |
| α-PAK | 419KRSTMVGTPYWMAPE423 | 22 |
| Ste20p | 770KPTTMVGTPYWMAPE784 | 23 |
Phosphorylation of the underlined residues is required for activity. Phosphorylation of the double underlined residues is presumed to be required for activity based on the effects of amino acid substitutions (see text). The residues in S6/H4 are numbered by analogy to PAK 65 (24).