Plants sequences

Fig. 3. Plastocyanin amino-acid sequences relevant to this review. Other sequence information is included. There are now 24 known sequences (18 formerly in Ref. [ I]). The 23 residues invariant throughout all 24 known higher plant and algal plastocyanin sequences are indicated ( ), 5 others (A) are invariant if A. variabilis is excluded, and a further 19 (o) if only the higher plant sequences are considered. Eieletions are indicated ( ), and residues which coordinate the Cu(V)...

The deduced sequence of D1 from Scenedesmus obliquus is more closely related to the sequences found in Chiamydomonas and higher plants than to members of other photosynthetic groups. However Scenedesmus appears to have retained a feature of Cyanobacteria and Prochlorophyta which is the lysine residue at position 238 this residue is arginine in most known higher plant sequences. This lysine residue was predicted in Scenedesmus because of the susceptibility of the D1 protein to digestion by the endoprotease lys-c (5,7). 

The preliminary alignment of the primary sequences was carried out with reference to known highly conserved homology blocks (H.C. Watson personal communication). These include those residues around the active site as defined for the yeast enzyme (see e.g. 6). The 3- dimensional structures were built using the programme FRODO. Where the plant sequence contained an amino acid which could not... 

Saxena I.M., and Brown, Jr. R.M., 1997. Identification of cellulose synthase(s) in higher plants sequence analysis of processive P-glycosyltransferases with the common motif D,D,D35Q(R,Q)XRW. Cellulose 4 33 9. 

Tabk I shows the rq)lacement of amino add residues by nonsynonymous nucleotide substitutions in the S conserved amino add sequences on the ALS enzyme. The alteration of tyrosine (Y) to histidine (H) in the first amino acid sequence (1) of R on A was found in 1 resistant bio pe. But it seems tiiat this replacement does not confer resistance, because the other resistant biotypes did not have such a replacement All S resistant biotypes had various point mutations (A, S, L) in the codon for a proline residue (P) in the second amino acid sequence (2) of Region A, whereas all 7 susceptible biotypes had the proline residue (P). Because this proline codon (P) is common with oth susceptible plants sequenced so far, it is possible tiiat its replacement confers resistance to SU herbicides in L, micrantha. Finalty, all of the resistant plants had an alteration from proline (P) to s me (A), alanine (S), or lysine (L) compared with the amino acid sequence of susceptible plants reported. 

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