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What are MIPs?
The Major Intrinsic Protein (MIPs) belong to the superfamily of proteins which transport water as well as other neutral molecules across the cell membrane. Functionaly they are devided in two broad groups:
Aquaporin: Pure water channels and Aquaglyceroporin: They can transport other neutral molecules also like glycerol.
What are the organisms for which MIPs have been identified?
The Major Intrinsic Proteins (MIPs) in MIPModDB belong to those species for which genome sequencing has been completed. The aquaporins were idetified from their genome sequence in NCBI itself using a protocol and were modelled by similar method as discussed in references given.
Do they represent the complete sets of MIPs for these organisms?
The identification of MIPs has been carried out from the available completed genome sequences which have been annotated. The correctness nad completeness of genome annotations are thus dependent on database itself. The unannotated might be the one missing in the identification process carried.
What is selectivity filter?
Selectivity filter is the narrowest region inside the channel. It is present nearly 8 A above the central pore in pure water transporting channel. It is mainly formed by four residues which line the channel. Two of these residues are contributed by loopE while other two residues come from helix2 and helix5.
What is meant by variations in NPA motif?
The NPA motif, contributed by two half helices of loopB and loopE are found to be highly conserved in MIPs. The, asparagine also forms hydrogen bonds with the water molecules crossing the channel. However, as the knowledge in MIPs increase, several exceptions to this conserved motif were observed. In present database, the MIPs can be identified with those variations (exceptions). They can be searched for variation in loopB motif and in loopE motif.
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