( Titin ( ( is ( the ( ( largest known ) protein ) ) ) ; ) )
(ROOT (S (NP (NNP Titin)) (VP (VBZ is) (NP (DT the) (ADJP (JJS largest) (VBN known)) (NN protein))) (: ;)))
Titin is the largest known protein;
(ROOT (S (NP (DT The) (ADJP (JJS largest) (VBN known)) (NNS proteins)) (VP (VBP are) (VP (VBN called) (NP (NNS titins)))) (. .)))