Aplysia LAPS18-like protein (ApLLP)
Aplysia nucleolar protein ApLLP is a transcriptional activator, which binds to the cAMP- response element (CRE) and thus
induces ApC/EBP expression required for establishing long-term memory.
All three ApLLP forms had the far-UV CD spectra typical of a highly unstructured protein lacking of any predominant secondary
ApLLP is capable of binding the CRE DNA element but this induces no significant change in its secondary and tertiary
structures. No significant increase in the HSQC spectral dispersion was observed for ApLLP-87 in complex with DNA, indicating
that the binding would not induce the formation of the tight tertiary packing. The far-UV CD spectrum only underwent very minor
changes, indicating that the secondary structure changes of ApLLP-87 triggered by DNA-binding were very subtle.
The DNA-binding residues are mainly located on the C-half of the ApLLP molecule, involving a lysine rich motif. This plays a
critical role in interacting with the CRE DNA sequence.
Fuzziness of ApLLP might enable dynamic regulation of synaptic facilitation in Aplysis neurons.