Data from: A new subfamily LIP of the major intrinsic proteins

Background: Proteins of the major intrinsic protein (MIP) family, or
aquaporins, have been detected in almost all organisms. These proteins are
important in cells and organisms because they allow for passive
transmembrane transport of water and other small, uncharged polar
molecules. Results: We compared the predicted amino acid sequences of 20
MIPs from several algae species of the phylum Heterokontophyta (Kingdom
Chromista) with the sequences of MIPs from other organisms. Multiple
sequence alignments revealed motifs that were homologous to functionally
important NPA motifs and the so-called ar/R-selective filter of
glyceroporins and aquaporins. The MIP sequences of the studied chromists
fell into several clusters that belonged to different groups of MIPs from
a wide variety of organisms from different Kingdoms. Two of these proteins
belong to Plasma membrane intrinsic proteins (PIPs), four of them belong
to GlpF-like intrinsic proteins (GIPs), and one of them belongs to a
specific MIPE subfamily from green algae. Three proteins belong to the
unclassified MIPs, two of which are of bacterial origin. Eight of the
studied MIPs contain an NPM-motif in place of the second conserved
NPA-motif typical of the majority of MIPs. The MIPs of heterokonts within
all detected clusters can differ from other MIPs in the same cluster
regarding the structure of the ar/R-selective filter and other generally
conserved motifs. Conclusion: We proposed placing nine MIPs from
heterokonts into a new group, which we have named the LIPs (large
intrinsic proteins). The possible substrate specificities of the studied
MIPs are discussed.