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Comparison of the specificities of p70 S6 kinase and MAPKAP kinase‐1 identifies a relatively specific substrate for p70 S6 kinase: the N‐terminal kinase domain of MAPKAP kinase‐1 is essential for peptide phosphorylation
Author(s) -
Leighton Ian A.,
Dalby Kevin N.,
Barry Caudwell F.,
Cohen Patricia T.W.,
Cohen Philip
Publication year - 1995
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(95)01170-j
Subject(s) - mitogen activated protein kinase kinase , kinase , p70 s6 kinase 1 , protein kinase domain , cyclin dependent kinase 9 , chemistry , map2k7 , map kinase kinase kinase , cyclin dependent kinase 2 , biochemistry , protein kinase a , phosphorylation , protein kinase b , mutant , gene
xxR/KxRxxSxx sequences were phosphorylated with high efficiency by both p70 S6 kinase (p70 S6K ) and MAPKAP kinase‐1. The best substrate for MAPKAP kinase‐1 (KKKNRTLSVA) was phosphorylated with a K m of 0.17 μM, and the best substrate for p70 S6K (KKRNRTLSVA) with a K m of 1.5 μM. The requirement of both enzymes for Arg/Lys at position n ‐5 could be partially replaced by inserting basic residues at other positions, especially by an Arg at n ‐ 2 or n ‐ 4. MAPKAP kinase‐1 (but not p70 S6K ) tolerated lack of any residue at n ‐ 5 if Arg was present at n ‐ 2 and n ‐ 3. p70 S6K (but not p90 S6K ) tolerated Thr at position n and absence of any residue at n + 2. The peptide KKRNRTLTV, which combined these features, was relatively selective for p70 S6K having a 50‐fold higher V max / K m than MAPKAP kinase‐1. Inactivation of the N‐terminal kinase domain of MAPKAP kinase‐1, which is 60% identical to p70 S6K , abolished activity towards all peptides tested, but the enzyme retained 30–40% of its activity if the C‐terminal kinase domain was inactivated.