Limits...
Molecular characterization of abLIM, a novel actin-binding and double zinc finger protein.

Roof DJ, Hayes A, Adamian M, Chishti AH, Li T - J. Cell Biol. (1997)

Bottom Line: However, a polypeptide corresponding to the full-length isoform is found exclusively in the retina and is enriched in biochemical extracts of retinal rod inner segments. abLIM protein also undergoes extensive phosphorylation in light-adapted retinas in vivo, and its developmental expression in the retina coincides with the elaboration of photoreceptor inner and outer segments.Based on the composite primary structure of abLIM protein, actin-binding capacity, potential regulation via phosphorylation, and isoform expression pattern, we speculate that abLIM may play a general role in bridging the actin-based cytoskeleton with an array of potential LIM protein-binding partners.The developmental time course of abLIM expression in the retina suggests that the retina-specific isoform may have a specialized role in the development or elaboration of photoreceptor inner and outer segments.

View Article: PubMed Central - PubMed

Affiliation: Berman-Gund Laboratory for the Study of Retinal Degenerations, Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts 02114, USA.

ABSTRACT
Molecules that couple the actin-based cytoskeleton to intracellular signaling pathways are central to the processes of cellular morphogenesis and differentiation. We have characterized a novel protein, the actin-binding LIM (abLIM) protein, which could mediate such interactions between actin filaments and cytoplasmic targets. abLIM protein consists of a COOH-terminal cytoskeletal domain that is fused to an NH2-terminal domain consisting of four double zinc finger motifs. The cytoskeletal domain is approximately 50% identical to erythrocyte dematin, an actin-bundling protein of the red cell membrane skeleton, while the zinc finger domains conform to the LIM motif consensus sequence. In vitro expression studies demonstrate that abLIM protein can bind to F-actin through the dematin-like domain. Transcripts corresponding to three distinct isoforms have a widespread tissue distribution. However, a polypeptide corresponding to the full-length isoform is found exclusively in the retina and is enriched in biochemical extracts of retinal rod inner segments. abLIM protein also undergoes extensive phosphorylation in light-adapted retinas in vivo, and its developmental expression in the retina coincides with the elaboration of photoreceptor inner and outer segments. Based on the composite primary structure of abLIM protein, actin-binding capacity, potential regulation via phosphorylation, and isoform expression pattern, we speculate that abLIM may play a general role in bridging the actin-based cytoskeleton with an array of potential LIM protein-binding partners. The developmental time course of abLIM expression in the retina suggests that the retina-specific isoform may have a specialized role in the development or elaboration of photoreceptor inner and outer segments.

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Nucleotide and derived amino acid sequences of  abLIM. Translation initiation sites for the three isoforms are indicated by the circled methionine residues. The abLIM-s isoform  contains a unique 5′ UTR that consists of 164 nt inserted 5′ to nt  1,012 and numbered −1 to −164 (see Materials and Methods).  The four LIM domains are shaded, the sequence that is deleted in  the abLIM-m isoform is underlined, and the 38–amino acid polymorphism (variably present in all isoforms) is indicated by a  dashed underline. (Arrow) Sequence provided by 5′ RACE.  These sequence data are available from GenBank/EMBL/DDBJ  under accession number AF005654.
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Figure 1: Nucleotide and derived amino acid sequences of abLIM. Translation initiation sites for the three isoforms are indicated by the circled methionine residues. The abLIM-s isoform contains a unique 5′ UTR that consists of 164 nt inserted 5′ to nt 1,012 and numbered −1 to −164 (see Materials and Methods). The four LIM domains are shaded, the sequence that is deleted in the abLIM-m isoform is underlined, and the 38–amino acid polymorphism (variably present in all isoforms) is indicated by a dashed underline. (Arrow) Sequence provided by 5′ RACE. These sequence data are available from GenBank/EMBL/DDBJ under accession number AF005654.

Mentions: Approximately 40 bp at the extreme 5′ end of the putative transcript were not present in any of the cDNA clones and were provided by subsequent 5′ RACE (Frohman et al., 1988) using sequence-specific primers (Fig. 1, arrow). The site of translation initiation is inferred from the presence of an in-frame stop codon 5′ to the putative methionine initiation codon. An open reading frame of 2,334 bp encodes a polypeptide of 778 amino acids with a predicted mass of 87.7 kD (Fig. 1). This polypeptide was named actin-binding LIM, or abLIM, protein based on two features of its primary sequence (see below).


Molecular characterization of abLIM, a novel actin-binding and double zinc finger protein.

Roof DJ, Hayes A, Adamian M, Chishti AH, Li T - J. Cell Biol. (1997)

Nucleotide and derived amino acid sequences of  abLIM. Translation initiation sites for the three isoforms are indicated by the circled methionine residues. The abLIM-s isoform  contains a unique 5′ UTR that consists of 164 nt inserted 5′ to nt  1,012 and numbered −1 to −164 (see Materials and Methods).  The four LIM domains are shaded, the sequence that is deleted in  the abLIM-m isoform is underlined, and the 38–amino acid polymorphism (variably present in all isoforms) is indicated by a  dashed underline. (Arrow) Sequence provided by 5′ RACE.  These sequence data are available from GenBank/EMBL/DDBJ  under accession number AF005654.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2141644&req=5

Figure 1: Nucleotide and derived amino acid sequences of abLIM. Translation initiation sites for the three isoforms are indicated by the circled methionine residues. The abLIM-s isoform contains a unique 5′ UTR that consists of 164 nt inserted 5′ to nt 1,012 and numbered −1 to −164 (see Materials and Methods). The four LIM domains are shaded, the sequence that is deleted in the abLIM-m isoform is underlined, and the 38–amino acid polymorphism (variably present in all isoforms) is indicated by a dashed underline. (Arrow) Sequence provided by 5′ RACE. These sequence data are available from GenBank/EMBL/DDBJ under accession number AF005654.
Mentions: Approximately 40 bp at the extreme 5′ end of the putative transcript were not present in any of the cDNA clones and were provided by subsequent 5′ RACE (Frohman et al., 1988) using sequence-specific primers (Fig. 1, arrow). The site of translation initiation is inferred from the presence of an in-frame stop codon 5′ to the putative methionine initiation codon. An open reading frame of 2,334 bp encodes a polypeptide of 778 amino acids with a predicted mass of 87.7 kD (Fig. 1). This polypeptide was named actin-binding LIM, or abLIM, protein based on two features of its primary sequence (see below).

Bottom Line: However, a polypeptide corresponding to the full-length isoform is found exclusively in the retina and is enriched in biochemical extracts of retinal rod inner segments. abLIM protein also undergoes extensive phosphorylation in light-adapted retinas in vivo, and its developmental expression in the retina coincides with the elaboration of photoreceptor inner and outer segments.Based on the composite primary structure of abLIM protein, actin-binding capacity, potential regulation via phosphorylation, and isoform expression pattern, we speculate that abLIM may play a general role in bridging the actin-based cytoskeleton with an array of potential LIM protein-binding partners.The developmental time course of abLIM expression in the retina suggests that the retina-specific isoform may have a specialized role in the development or elaboration of photoreceptor inner and outer segments.

View Article: PubMed Central - PubMed

Affiliation: Berman-Gund Laboratory for the Study of Retinal Degenerations, Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts 02114, USA.

ABSTRACT
Molecules that couple the actin-based cytoskeleton to intracellular signaling pathways are central to the processes of cellular morphogenesis and differentiation. We have characterized a novel protein, the actin-binding LIM (abLIM) protein, which could mediate such interactions between actin filaments and cytoplasmic targets. abLIM protein consists of a COOH-terminal cytoskeletal domain that is fused to an NH2-terminal domain consisting of four double zinc finger motifs. The cytoskeletal domain is approximately 50% identical to erythrocyte dematin, an actin-bundling protein of the red cell membrane skeleton, while the zinc finger domains conform to the LIM motif consensus sequence. In vitro expression studies demonstrate that abLIM protein can bind to F-actin through the dematin-like domain. Transcripts corresponding to three distinct isoforms have a widespread tissue distribution. However, a polypeptide corresponding to the full-length isoform is found exclusively in the retina and is enriched in biochemical extracts of retinal rod inner segments. abLIM protein also undergoes extensive phosphorylation in light-adapted retinas in vivo, and its developmental expression in the retina coincides with the elaboration of photoreceptor inner and outer segments. Based on the composite primary structure of abLIM protein, actin-binding capacity, potential regulation via phosphorylation, and isoform expression pattern, we speculate that abLIM may play a general role in bridging the actin-based cytoskeleton with an array of potential LIM protein-binding partners. The developmental time course of abLIM expression in the retina suggests that the retina-specific isoform may have a specialized role in the development or elaboration of photoreceptor inner and outer segments.

Show MeSH