Locusta migratoria apolipophorin III (apoLp-III) is an exchangeable apolipoprotein that aids in the transport of diacylglycerol through the hemolymph of insects. The x-ray structure shows five α-helices which form a five helix bundle. The NMR solution structure revealed the presence of a four-residue mini-helix that was not identified in the x-ray structure. It was hypothesized that this mini-helix initiates lipid binding. Mutant apoLp-III was generated in which the mini-helix (AWAP) was converted into a β-turn (NPNG). The mutation led to some changes in protein structure, but the overall tertiary structure was maintained. Lipid binding studies revealed that the rate of discoidal lipoprotein formation increased for all variants. However, W130Q and NPNG apoLp-III were not able to bind low-density lipoproteins as well as wild-type apoLp-III. Based on our data, it was concluded that the mini-helix does not initiate lipid binding.
|Advisor:||Weers, Paul M. M.|
|Commitee:||Narayanaswami, Vasanthy, Schwans, Jason|
|School:||California State University, Long Beach|
|Department:||Chemistry and Biochemistry|
|School Location:||United States -- California|
|Source:||MAI 53/01M(E), Masters Abstracts International|
|Keywords:||Apoliophorin III, Apolipoprotein, Lipid transport and binding, Locusta migratoria, Mini-helix|
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