Determinants of type-specificity. Alignment of amino acid sequences in surface-exposed loops of capsid proteins L1 of HPV16 and HPV33. Divergent amino acids are listed; identical amino acids are marked by asterisks. On the right, localization of these hyper variable loops in the L1 monomer is shown. Modeling by RasMol was based on the monomeric structure of the HPV16 capsid protein L1.