The 44‐kDa Regulatory Subunit of the Paramecium cAMP‐Dependent Protein Kinase Lacks a Dimerization Domain and May Have a Unique Autophosphorylation Site Sequence

Abstract

The 44-kDa regulatory subunit (R44) of one form of cAMP-dependent protein kinase of Paramecium was purified, and two partial internal amino acid sequences from it were used to clone the corresponding cDNA. This R44 cDNA clone was 1022-bp long, including 978 bp of coding sequence and 7 bp and 37 bp of 5' and 3' untranslated sequences, respectively. A 1.1-kb mRNA was labeled on a Northern blot. The deduced R44 amino acid sequence had 31%-38% positional identity to the sequences of other cloned cAMP-dependent protein kinase regulatory subunits. R44 sequence showed equal sequence similarity to mammalian types I and II regulatory subunits. The N-terminal sequence encoding the regulatory subunit dimerization domain found in most regulatory subunits is not present in the R44 clone, confirming the lack of regulatory subunit dimer formation previously reported for the Paramecium cAMP-dependent protein kinase. The putative autophosphorylation site of R44 contains the amino acid sequence TRTS, distinct from the consensus sequence RRXS, where X is any residue, found in other autophosphorylated cAMP-dependent protein kinase regulatory subunits and many cAMP-dependent protein kinase substrates.

Calmodulin and PF6 are components of a complex that localizes to the C1 microtubule of the flagellar central apparatus

“…The lack of an intact regulatory RII dimerization domain does not preclude a role for PF6-IP1 as a PKA regulatory subunit, as PKAs of both Paramecium and Dictyostelium have subunits that do not have RII domains (Mutzel et al, 1987;Carlson and Nelson, 1996). In addition, the leucinerich repeat region of PF6-IP1 aligns with the CAP_ED domain of the Trypanosoma predicted regulatory subunit (29% identity, 51% similarity).…”

Classification and Phylogenetic Analysis of the cAMP-Dependent Protein Kinase Regulatory Subunit Family

“…In all the subunits from Fungi and type I subunits, the ⌿ residue was followed by a serine, whereas in all type II subunits that position was occupied by a cysteine. The R subunit from the ciliate Paramecium tetraurelia contains an atypical inhibitory sequence conforming to the pattern TRxS⌿ (Carlson and Nelson 1996). When the R subunit from Euplotes octocarinatus was scanned for suitable PKA phosphorylation sites that could function as inhibitory sequences, a novel sequence corresponding to the motif KxS⌿ was identified (Fig.…”

Analysis of Micronuclear, Macronuclear and cDNA Sequences Encoding the Regulatory Subunit of cAMP‐Dependent Protein Kinase of Euplotes octocarinatus: Evidence for a Ribosomal Frameshift

“…Hochstrasser et al 1996; Mason and Nelson 1989). Cloning of the gene encoding R 44 showed that this subunit lacks a dimerization domain (Carlson and Nelson 1996). As a result, the corresponding PKA forms a RC heterodimer domain (Carlson and Nelson 1996), as is the case in Dictyostelium discoideum (Mutzel et al 1987).…”

“…Cloning of the gene encoding R 44 showed that this subunit lacks a dimerization domain (Carlson and Nelson 1996). As a result, the corresponding PKA forms a RC heterodimer domain (Carlson and Nelson 1996), as is the case in Dictyostelium discoideum (Mutzel et al 1987). In addition, the autophosphorylation site TRTSV of R 44 does not match the consensus motif RRXSZ of all other autophosphorylated PKA R subunits.…”