An evolutionarily conserved cyclin homolog from Drosophila rescues yeast deficient in G1 cyclins - PubMed (original) (raw)

Figure 3. Cyclin C Sequence Alignment with Conserved Cyclin Sequences

The bars in the upper panel are scaled representations of five divergent cyclins. The location of the three regions identified as having high conservation are indicated as shaded segments. The scale is indicated on the right. For each of the conserved regions, a consensus of G2 cyclin sequences is shown. This was derived as follows: 15 G2 cyclin sequences were compared (clam cyclins A [Swenson et al., 1986] and B [Westendorf et al., 1989], human cyclins A [Wang et al., 1990] and B [Pines and Hunter, 1989], Drosophila cyclins A [Lehner and O’Farrell, 1989] and B [Lehner and O’Farrell, 1990], frog cyclins A [Minshull et al., 1990], B1 [Minshull et al., 1989], and B2 [Minshull et al., 1989], sea urchin cyclin [Pines and Hunt, 1987], S. pombe cdc13 [Booher and Beach, 1988], and S. cerevisiae Clb1, Clb2, Clb3, and Clb4 [Ghiara et al., 1991]). At each position, the most commonly occurring amino acid was selected for the consensus. In the few cases of a numerical tie, we selected the residue that was the most widely distributed among the more evolutionarily diverged cyclins. Below the consensus, all of the different residues that occur at a position are listed as alternatives. The cyclin C sequence and the other diverged cyclin sequences were aligned with the G2 consensus sequence. The number to the left of each aligned sequence is the position of the first residue of the segment. As a reference and an example of a G2 cyclin, the clam cyclin A sequence is included in this alignment. Residues matching the G2 consensus are boxed and shaded. Residues considered homologous to the residues of the consensus are boxed, according to the following groupings: A, L, V, I, M; D, E; K, R; N, Q; F, Y; S, T. The scores on the right of each alignment were calculated as follows. The 15 G2 sequences were used as a reference. The number of times each amino acid occurred at a given position in this reference set was determined. For an aligned sequence, each position was given a score corresponding to the number of times the corresponding amino acid occurred in the reference set. The total scores for an alignment were then normalized by dividing by the maximum score (number of positions scored × number of sequences in the reference set). For the ras homology within region III, homology scores were similarly calculated based only on the 21 amino acid sequence indicated for human H-ras.