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Fig. 1. Sequence analysis of Gyc-88E and Gyc-89Db. (A)
Intron/exon structure and splice variants of the coding region of Gyc-88E.
Exons are represented by boxes while introns are indicated with lines. The
guanylyl cyclase functional domains are also indicated. The two splice
variants are generated through the use of alternative splice/donor sites to
vary how exons 10 and 11 are connected to yield Gyc-88E-S and
Gyc-88E-L, which includes an additional 21 bp. The extra 21 bp in
Gyc-88E-L translates into a seven amino acid stretch that contains
potential PKC and PKG phosphorylation motifs, KITFS and KKIT, respectively.
(B) Multiple sequence alignment of Gyc-88E and Gyc-89Db with selected atypical
guanylyl cyclase subunits. The other sequences included in the alignment are
MsGC-ß3 (Nighorn et al.,
1999), CP12881, the predicted orthologue of MsGC-ß3 in
Anopheles gambiae (accession number EAA01162), and the rat ß2
subunit. Gyc-88E shares a high degree of sequence identity over the N-terminal
and catalytic domains with MsGC-ß3 and CP12881, whereas the C-terminal
domains are more divergent, except for two highly conserved sections of 21 and
10 amino acids (underlined). Gyc-88E, MsGC-ß3, CP12881 and the rat
ß2 subunit all have the necessary catalytic residues (marked `B' for
ß subunit residues and `A' for 
subunit residues) that are
predicted to be required for forming an active homodimer (see
Morton and Hudson, 2002 for a
more extensive discussion). By contrast, Gyc-89Db has the residues
characteristic of a ß subunit but is lacking some of those necessary for
an subunit. All four of the insect subunits shown lack two cysteine
residues (indicated with asterisks) required for NO activation, which are
present in the rat ß2 subunit. A histidine residue, thought to be the
axial ligand for the heme group in conventional /ß heterodimers
(Zhao et al., 1998), is
present in all of the subunits shown (indicated with a `+').
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