146 

 established in the literature is shown in Table 7-4. The 

 transit peptides vary from 34 to 88 amino acid residues. 

 The sequence context around the translation start (AUG) is 

 proposed to most often be AACAAUGGC in plant genes (54) . 

 Included in this survey are the seven known sequences for 

 aromatic pathway proteins. From this selection in Table 7- 

 4, only one of sixteen, chorismate synthase in barley 

 (aromatic pathway protein) has this proposed conserved 

 region. The cleavage site often exhibits the pattern (V/I)- 

 X- (A/C) iA, with R frequently at position -2 or between -6 to 

 -10 (33) . Of the seven aromatic pathway proteins, shikimate 

 kinase in tomato conforms to the motif before the cleavage 

 point and five of the remaining nine sequences conform to 

 the cleavage point (two of these also have the proposed ALA 

 after the cleavage point) . The S-protein does not fit this 

 cleavage site motif. The overall features of transit 

 peptides, show that they are rich in hydroxylated amino 

 acids, SER and THR (20-35%) , small hydrophobic amino acids 

 such as VAL and ALA, not especially rich in basic amino 

 acids (but do have a net positive charge) , and usually have 

 only one or two acidic groups (45) . The aromatic pathway 

 protein transit peptides follow these features, being 

 especially rich in SER. The S-protein truncated transit 

 peptide (23 residues) has 17% SER (3) and THR (1), 35% 

 hydrophobic residues, 0.09% basic residues {R (ARG) and K 

 (LYS) near the cleavage point} and 13% acidic residues. 



