AAV capsid proteins

The structural proteins of AAV particles have been dissociated with sodium dodecyl sulfate (SDS) or urea and then separated by polyacrylamide gel electrophoresis (Johnson and Hoggan, 1971 Rose et al., 1971). Three proteins were identified with estimated molecular weights of 62-66000 73-80000 and 87-92000, respectively. The smallest polypeptide represented about 80% of the total protein mass while the other two represented approximately 10% each. There was no correspondence in electrophoretic mobility with adenovirus structural proteins except that there was a partial overlap of the major AAV protein and the adenovirus fiber penton. The three AAV capsid proteins were present in all three human serotypes (AAV I-3) and had similar mobilities with the exception that the major protein species of AAV 2 moved slightly faster than the comparable AAV 1 and 3 species. Very minor... 

Stocks are analyzed by silver or Coomassie blue staining of capsid proteins separated on SDS polyacrylamide gels. As shown in Fig. 2.4A, the three capsid proteins (VP1, 2, and 3) are visible in the correct stoichiometry of 1 1 10, and are free of non-AAV proteins (>95% pure). 

AAV 1-4 are serologically distinct although AAV 2 and 3 cross-react (Hoggan, 1970). Because the DNAS of the four serotypes have 30-50% of nucleotide sequences in common it might be expected that there would be some amino acid sequences of the structural proteins of the different serotypes which would be similar. Common amino acid sequences may not be exposed in the tertiary structure assumed by the capsid proteins. Support for this suggestion has been provided by the data of Johnson et al. (1972). These authors prepared antisera to the three structural proteins of AAV-3 after SDS treatment. Antisera to the SDS-polypeptides did not interact with intact virions, but the antisera raised against specific AAV-3 SDS-polypeptides did react with the analogous SDS-polypeptides of AAV-1 and AAV-2. 

AAV virions are small nonenveloped particles (20-25 nm) that carry a linear single-stranded DNA (ssDNA) genome, which is 4.7 kb in size. Two open reading frames (ORFs), rep and cap, have been identified in the viral genome and are flanked by T-shaped inverted terminal repeats (ITRs). The cap ORF encodes for the structural proteins that form the capsid, whereas the regulatoiy proteins are produced from the rep ORF (Figure L4). [For more details see (1).]... 

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