3.5. Sequence analysis of the partial cDNA fragment encoding a
petal cysteine peptidase
A 711 bp cDNA fragment, from a gene encoding a cysteine peptidase
was identified in the cDNA of senescent petals of Dendrobium
cv. Khao Sanan flowers. The isolated fragmentwas called Den-Cys1.
Its accession number is EU152214.
The deduced amino acid sequence (171 aa) contained two
catalytic active sites: the cysteine-peptidase histidine active site
(amino acid sequence: LDHGVAIVGYG, starting at residue 97 from
the onset of the isolated fragment) and the cysteine-peptidase
asparagine active site (amino acid sequence: YWIVRNSWGPEWGEKGYIRM,
starting at residue 117 from the onset of the
fragment). Seven amino acidswere present between the two active
sites. The third active site (cysteine active site, amino acid sequence
QGQCGSCWAFST) of the typical catalytic triad in cysteine peptidases
was not found in the present fragment. The deduced amino
acid sequence of the present fragment did have an endoplasmic
reticulum retaining targeting sequence (amino acid sequence
KDEL) at its C terminal end. The sequenced fragment shared 85% of
its nucleotide sequence with a Phalaenopsis cysteine peptidase (full
cds, accession PSU34747).