Analysis of septins across kingdoms reveals orthology and new motifs.
BACKGROUND
Septins are cytoskeletal GTPase proteins first discovered in the fungus Saccharomyces cerevisiae where they organize the septum and link nuclear division with cell division. More recently septins have been found in animals where they are important in processes ranging from actin and microtubule organization to embryonic patterning and where defects in septins have been implicated in human disease. Previous studies suggested that many animal septins fell into independent evolutionary groups, confounding cross-kingdom comparison.


RESULTS
In the current work, we identified 162 septins from fungi, microsporidia and animals and analyzed their phylogenetic relationships. There was support for five groups of septins with orthology between kingdoms. Group 1 (which includes S. cerevisiae Cdc10p and human Sept9) and Group 2 (which includes S. cerevisiae Cdc3p and human Sept7) contain sequences from fungi and animals. Group 3 (which includes S. cerevisiae Cdc11p) and Group 4 (which includes S. cerevisiae Cdc12p) contain sequences from fungi and microsporidia. Group 5 (which includes Aspergillus nidulans AspE) contains sequences from filamentous fungi. We suggest a modified nomenclature based on these phylogenetic relationships. Comparative sequence alignments revealed septin derivatives of already known G1, G3 and G4 GTPase motifs, four new motifs from two to twelve amino acids long and six conserved single amino acid positions. One of these new motifs is septin-specific and several are group specific.


CONCLUSIONS
Our studies provide an evolutionary history for this important family of proteins and a framework and consistent nomenclature for comparison of septin orthologs across kingdoms.
Pan
Fangfang
F
Plant Biology Department, University of Georgia, Athens, GA 30602, USA. fpan@plantbio.uga.edu <fpan@plantbio.uga.edu>
Malmberg
Russell L
RL
Momany
Michelle
M
D020816:Amino Acid Motifs / Q000235:genetics; D000818:Animals; D029742:Caenorhabditis elegans Proteins / Q000737:chemistry / Q000235:genetics; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000145:classification / Q000235:genetics*; D016384:Consensus Sequence; D017124:Conserved Sequence; D003598:Cytoskeletal Proteins / Q000737:chemistry / Q000145:classification / Q000235:genetics*; D029721:Drosophila Proteins / Q000737:chemistry / Q000235:genetics; D019143:Evolution, Molecular; D005656:Fungal Proteins / Q000737:chemistry / Q000145:classification / Q000235:genetics; D005658:Fungi / Q000201:enzymology / Q000235:genetics; D020558:GTP Phosphohydrolases / Q000737:chemistry / Q000145:classification / Q000235:genetics*; D020440:Gene Duplication; D006801:Humans; D019476:Insect Proteins / Q000737:chemistry / Q000235:genetics; D051379:Mice; D016814:Microsporidia / Q000201:enzymology / Q000235:genetics; D005810:Multigene Family; D010802:Phylogeny; D051304:Profilins / Q000737:chemistry / Q000235:genetics; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics; D017434:Protein Structure, Tertiary; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics; D051381:Rats; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D009626:Terminology as Topic; D029961:Zebrafish Proteins / Q000737:chemistry / Q000235:genetics
C086662:CDC3 protein, S cerevisiae; D029742:Caenorhabditis elegans Proteins; D018797:Cell Cycle Proteins; D003598:Cytoskeletal Proteins; D029721:Drosophila Proteins; D005656:Fungal Proteins; D019476:Insect Proteins; D051304:Profilins; D020033:Protein Isoforms; D015800:Protozoan Proteins; D029701:Saccharomyces cerevisiae Proteins; D029961:Zebrafish Proteins; D020558:GTP Phosphohydrolases