( ( ( ( ( ( Receptor-linked ( tyrosine kinases ) ) , ) ( Ras ( , ( Raf ( , ( MEK , ) ) ) ) ) ) and ) MAPK ) ( ( could ( be ( fitted ( into ( ( a ( signaling cascade ) ) ( ( linking ( an ( extracellular signal ) ) ) ( to ( MAPK activation ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (JJ Receptor-linked) (NN tyrosine) (NNS kinases)) (, ,) (NP (NNP Ras) (, ,) (NNP Raf) (, ,) (NNP MEK) (, ,)) (CC and) (NP (NNP MAPK))) (VP (MD could) (VP (VB be) (VP (VBN fitted) (PP (IN into) (NP (NP (DT a) (JJ signaling) (NN cascade)) (VP (VBG linking) (NP (DT an) (NN extracellular) (NN signal)) (PP (TO to) (NP (NN MAPK) (NN activation))))))))) (. .)))
Receptor-linked tyrosine kinases, Ras, Raf, MEK, and MAPK could be fitted into a signaling cascade linking an extracellular signal to MAPK activation.
(ROOT (S (NP (JJ Enzymatic) (NNS cascades)) (VP (VBP help) (VP (VB amplify) (NP (NP (DT the) (NNS effects)) (PP (IN of) (NP (NN extracellular) (NNS signals)))))) (. .)))