Algorithm 1 Mining Sequential Pattern (Note: min_support is the minimum support threshold, min_mon_wc is the minimal non-wildcard threshold, and last (a) is the last amino acid or nucleotides)

1: Mining ($a$,$S_a$)

2:  if |$S_a$| ≥ $\mathit{min}\_\mathit{support}$ then

3:    if $\mathit{non}\_\mathit{wc}$ ($a$) ≥ $\mathit{min}\_\mathit{mon}\_\mathit{wc}$ and last ($a$) ≠ $x$ then

4:     if $a$ is a closed pattern then

5:       report $a$, |$S_a$|

6:    for each residue $b$ or $x$ do

7:      $a^{\prime }$: = $a$ with $b$ or $x$ appended to it

8:      Mining ($a^{\prime }$,${S_a}^{\prime }$)