TMP-M2Align: A Topology-Aware Multiobjective Approach to the Multiple Sequence Alignment of Transmembrane Proteins

Transmembrane proteins (TMPs) constitute approximately 30% of the mammalian proteome and are critical targets in biomedical research due to their involvement in signaling, transport, and drug interactions. However, their unique structural characteristics pose significant challenges for conventional multiple sequence alignment (MSA) methods, which are typically optimized for soluble proteins. In this paper, we propose TMP-M2Align, a novel topology-aware multiobjective algorithm specifically designed for the multiple alignment of TMPs. The method simultaneously optimizes two complementary objectives: (i) a topology-aware Sum-of-Pairs (SPs) score that integrates region-specific substitution matrices and gap penalties, and (ii) an Aligned Regions (ARs) score that rewards consistent alignment of functional and topological domains. By combining these objectives, TMP-M2Align generates Pareto front approximations of alignment solutions, enabling researchers to select trade-offs that best suit their biological questions. We evaluated TMP-M2Align on BAliBASE Reference Set 7 and on complete datasets of human G protein-coupled receptors (GPCRs) from classes A, B1, and C. Experimental results demonstrate that TMP-M2Align consistently outperforms both traditional alignment tools and specialized TM-specific methods in terms of SPs and Total Column metrics. Moreover, qualitative topological analyses confirm that TMP-M2Align preserves the integrity of transmembrane helices and loop boundaries more effectively than competing approaches. These findings highlight the effectiveness of integrating topology-aware scoring with multiobjective optimization for achieving accurate and biologically meaningful alignments of TMPs.