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Main porin from Mycobacterium smegmatis (MspA)
Structural highlights
FunctionMSPA_MYCS2 The major porin in this organism, forms a water-filled channel which favors the permeation of cations, amino acids, iron Fe(3+) and less efficiently phosphate. Does not transport Fe-ExoMS, the predominant siderophore. Plays a role in transport of beta-lactamase and hydrophilic fluoroquinolone antibiotics such as norfloxacin as well as chloramphenicol. There are about 2400 porins in wild-type, 800 in an mspA deletion and 150 in a double mspA-mspC deletion. Different conductance values with maxima at 2.3 and 4.6 nanosiemens might be caused by a simultaneous reconstitution of MspA channels into the membrane or by the existence of different MspA conformations.[1] [2] [3] [4] [5] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedMycobacteria have low-permeability outer membranes that render them resistant to most antibiotics. Hydrophilic nutrients can enter by way of transmembrane-channel proteins called porins. An x-ray analysis of the main porin from Mycobacterium smegmatis, MspA, revealed a homooctameric goblet-like conformation with a single central channel. This is the first structure of a mycobacterial outer-membrane protein. No structure-related protein was found in the Protein Data Bank. MspA contains two consecutive beta barrels with nonpolar outer surfaces that form a ribbon around the porin, which is too narrow to fit the thickness of the mycobacterial outer membrane in contemporary models. The structure of a mycobacterial outer-membrane channel.,Faller M, Niederweis M, Schulz GE Science. 2004 Feb 20;303(5661):1189-92. PMID:14976314[6] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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