Amino acid sequence of the ribulose-1,5-bisphosphate carboxylase/oxygenase small subunit from Euglena

Abstract

The amino acid sequence of the ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) small subunit (SSU) from Euglena has been established by alignment of the sequence of peptides obtained by cleavage with chymotrypsin, trypsin, Staphylococcus aureus protease or formic acid. The Euglena SSU has 138 amino acids and thus represents longest SSU sequence described so far. Homology is only 41% with cyanobacteria SSU and about 51% with higher plant SSU, whereas it is around 75% between higher plants. The largest homologous portion between all the known SSU sequences is localized in the second half and covers about 20 amino acids. The phylogenetic tree based on known SSU sequences has been established and the rate of amino acid substitution for SSU is estimated to be about 1.35×10(-9) per year and per site. Despite heterogeneity in amino acid sequence, we found that the overall secondary structure is fairly well conserved.

The small subunit of ribulose-1,5-bisphosphate carboxylase is plastid-encoded in the chlorophyll c-containing alga Cryptomonas ?

“…When compared to the Fucus small subunit, however, 83 ~o similarity is observed. The similarity between land plant small subunits is usually greater than 70~o [18]. The Fucus sequence is much more closely related to that from Cryptomonas 4) than to those from any of the other organisms in the comparison.…”

“…Table 1 shows the percent similarity between the small subunit sequences from these sources. [ 15], Anacystis nidulans [20], Chlamydomonas reinhardtii [6], Euglena gracilis [18], Triticum aestivum [1], Nicotiana tabacum [12].…”

“…The amino-terminal 41 amino acids of the small subunit from Fucus have been shown to contains sections unlike either cyanobacteria, land plants or chlorophytic algae [7] and these are shared with Cryptomonas ¢. It is larger than other small subunits even though it does not contain the characteristic 7 amino acids which are present at There may be extra sequences at the carboxy terminus or internally as in Chlamydomonas reinhardtii [6] and Euglena gracilis [ 18]. The coding location of the Fucus gene (and thus the presence or absence of a signal peptide) is unknown.…”

Molecular cloning and nucleotide sequence of the psaA and psaB genes of the cyanobacterium Synechococcus sp. PCC 7002

“…Indeed, the E. gracilis psaA sequence appears to be no more homologous to the higher plant psaA sequences than to the cyanobacterial psaA sequence. The distinctive phylogenetic position of E. gracilis has been noted before in sequence comparisons of psaA [31], rbcL [19], and rbcS [52] gene products. The E. gracilis psaA gene does differ from all other psaA genes sequenced to date in having three introns [11].…”

Ribulose bisphosphate carboxylase in algae: synthesis, enzymology and evolution

“…In addition, the derived amino acid sequence of Olisthodiscus (Boczar et al 1989) and Cryptomonas (Douglas and Durnford 1989) Chromophytic and rhodophytic SS polypeptides show minimal similarity (20-40% identity) to chlorophytic plant and blue-green algal proteins (Boczar et al 1989). In contrast, land plant, green algal (Sailland et al 1986, Simard et al 1988) and blue-green algal Rubisco SS amino acid sequences are 40-78% similar (Miziorko and Lorimer 1983), although homologies are greater among organisms within a group than between groups (Simard et al 1988). Thus, chromophytic and rhodophytic SS polypeptides are more similar to each other (and to Alcaligenes) than they are to the cyanobacterial or chlorophytic plant Rubisco small subunits.…”