Further improvement in methods of group-to-group sequence alignment with generalized profile operations.

It has previously been shown that rigorous optimization of alignment between two groups of sequences in the sense of minimal sum of pairs (SP) score with a linear gap-weighting function can be achieved by an extended version of the dynamic programming algorithm. The major drawback of this algorithm was that the computation time grows in proportion to the product of the numbers (M and N) of sequences comprising the two groups. A new algorithm presented in this paper achieves the same rigorous alignment in a time complexity much less dependent on the sizes of the groups. Examinations with many groups of sequences indicated that the new algorithm runs faster than the earlier one when M x N > 6-10, approximately 10 times faster when M x N approximately 200, and > 100 times faster when M x N > 2500. This computational acceleration facilitates application of the algorithm to alignment of large groups, especially in the framework of iterative refinement strategies.