A novel plant major intrinsic protein in Physcomitrella patens most similar to bacterial glycerol channels.
A gene encoding a novel fifth type of major intrinsic protein (MIP) in plants has been identified in the moss Physcomitrella patens. Phylogenetic analyses show that this protein, GlpF-like intrinsic protein (GIP1;1), is closely related to a subclass of glycerol transporters in bacteria that in addition to glycerol are highly permeable to water. A likely explanation of the occurrence of this bacterial-like MIP in P. patens is horizontal gene transfer. The expressed P. patens GIP1;1 gene contains five introns and encodes a unique C-loop extension of approximately 110 amino acid residues that has no obvious similarity with any other known protein. Based on alignments and structural comparisons with other MIPs, GIP1;1 is suggested to have retained the permeability for glycerol but not for water. Studies on heterologously expressed GIP1;1 in Xenopus laevis oocytes confirm the predicted substrate specificity. Interestingly, proteins of one of the plant-specific subgroups of MIPs, the NOD26-like intrinsic proteins, are also facilitating the transport of glycerol and have previously been suggested to have evolved from a horizontally transferred bacterial gene. Further studies on localization and searches for GIP1;1 homologs in other plants will clarify the function and significance of this new plant MIP.
Gustavsson
Sofia
S
Department of Plant Biochemistry, Centre for Chemistry and Chemical Engineering, Lund University, Sweden.
Lebrun
Anne-Sophie
AS
Nordén
Kristina
K
Chaumont
François
F
Johanson
Urban
U
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D019068:Bryopsida / Q000235:genetics* / Q000378:metabolism; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D022761:Gene Transfer, Horizontal; D005990:Glycerol / Q000378:metabolism*; D008969:Molecular Sequence Data; D010802:Phylogeny; D010940:Plant Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
D001426:Bacterial Proteins; D018076:DNA, Complementary; D010940:Plant Proteins; D005990:Glycerol