The Importance of Conserved Features of Yeast Actin-Binding Protein 1 (Abp1p): The Conditional Nature of Essentiality

Abstract

Saccharomyces cerevisiae Actin-Binding Protein 1 (Abp1p) is a member of the Abp1 family of proteins, which are in diverse organisms including fungi, nematodes, flies, and mammals. All proteins in this family possess an N-terminal Actin Depolymerizing Factor Homology (ADF-H) domain, a central Proline-Rich Region (PRR), and a C-terminal SH3 domain. In this study, we employed sequence analysis to identify additional conserved features of the family, including sequences rich in proline, glutamic acid, serine, and threonine amino acids (PEST), which are found in all family members examined, and two motifs, Conserved Fungal Motifs 1 and 2 (CFM1 and CFM2), that are conserved in fungi. We also discovered that, similar to its mammalian homologs, Abp1p is phosphorylated in its PRR. This phosphorylation is mediated by the Cdc28p and Pho85p kinases, and it protects Abp1p from proteolysis mediated by the conserved PEST sequences. We provide evidence for an intramolecular interaction between the PRR region and SH3 domain that may be affected by phosphorylation. Although deletion of CFM1 alone caused no detectable phenotype in any genetic backgrounds or conditions tested, deletion of this motif resulted in a significant reduction of growth when it was combined with a deletion of the ADF-H domain. Importantly, this result demonstrates that deletion of highly conserved domains on its own may produce no phenotype unless the domains are assayed in conjunction with deletions of other functionally important elements within the same protein. Detection of this type of intragenic synthetic lethality provides an important approach for understanding the function of individual protein domains or motifs.

Protein context shapes the specificity of domain-peptide interactionsin vivo

“…A) Protein expression levels of the Abp1 SH3 swapped proteins for which the smallest number of DHFR-PCA PPIs were measured as compared to the Abp1 SH3 in Abp1 and SH3-deleted strains. Two bands are detected for Abp1, as previously observed (Garcia, Stollar and Davidson, 2012) . B) Number of PPIs that were affected by Abp1 SH3 domain swapping.…”

Phosphoproteome Analysis Links Protein Phosphorylation to Cellular Remodeling and Metabolic Adaptation during Magnaporthe oryzae Appressorium Development

“…Sc Abp1 binds filamentous actin (F-Actin), is a component of cortical actin patches involved in endocytosis and is important for activation of the Arp2/3 actin nucleating complex 107 . Sc Abp1 is a target of the Pho85 and Cdc28 kinases and its phosphorylation status influences its susceptibility to proteolytic degradation 108 . The coronin, Sc Crn1, and transgelin-like protein, Sc Scp1, produce F-actin bundles via a cross linking of filaments 109, 110 .…”

Phospho‐regulation of intrinsically disordered proteins for actin assembly and endocytosis

“…Why ABPs comprise many IDPs is still unclear, but it could involve protein-protein interactions that can be modulated in response to specific signaling cues, such as cell cycle progression, stress responses, or mating. Both Cdk1 and Pho85 phosphorylate Abp1, which physically interacts with Ark1 and Sla1, indicating a potential scaffolding function of Abp1 to facilitate the Ark1 phosphorylation of Sla1 [123]. In addition, a phosphorylation-regulated intramolecular interaction between the SH3 domain and polyproline domain has also been suggested for Sla1-Abp1 binding [123].…”