Structural highlights
Function
[UNC89_CAEEL] Structural component of the muscle M-line. Myofilament lattice assembly begins with positional cues laid down in the basement membrane and muscle cell membrane. UNC-89 responds to these signals, localizes, and then participates in assembling an M-line.[1] [2]
Publication Abstract from PubMed
BACKGROUND: Pleckstrin homology (PH) domains constitute a structurally conserved family present in many signaling and regulatory proteins. PH domains have been shown to bind to phospholipids, and many function in membrane targeting. They generally have a strong electrostatic polarization and interact with negatively charged phospholipids via the positive pole. On the basis of electrostatic modeling, however, we have previously identified a class of PH domains with a predominantly negative charge and predicted that these domains recognize other targets. Here, we report the first experimental structure of such a PH domain. RESULTS: The structure of the PH domain from Caenorhabditis elegans muscle protein UNC-89 has been determined by heteronuclear NMR. The domain adopts the classic PH fold, but has an unusual closed conformation of the "inositol binding loops. This creates a small opening to a deep hydrophobic pocket lined with negative charges on one side, and provides a molecular explanation for the lack of association with inositol-1,4,5-triphosphate. As predicted, the PH domain of UNC-89 has a strongly negative overall electrostatic potential. Modeling the Dbl homology (DH)-linked PH domains from the C. elegans genome shows that a large proportion of these modules are negatively charged. CONCLUSIONS: We present the first structure of a PH domain with a strong negative overall electrostatic potential. The presence of a deep pocket lined with negative charges suggests that the domain binds to ligands other than acidic phospholipids. The abundance of this class of PH domain in the C. elegans genome suggests a prominent role in mediating protein-protein interactions.
Structure of a PH domain from the C. elegans muscle protein UNC-89 suggests a novel function.,Blomberg N, Baraldi E, Sattler M, Saraste M, Nilges M Structure. 2000 Oct 15;8(10):1079-87. PMID:11080629[3]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Benian GM, Tinley TL, Tang X, Borodovsky M. The Caenorhabditis elegans gene unc-89, required fpr muscle M-line assembly, encodes a giant modular protein composed of Ig and signal transduction domains. J Cell Biol. 1996 Mar;132(5):835-48. PMID:8603916
- ↑ Small TM, Gernert KM, Flaherty DB, Mercer KB, Borodovsky M, Benian GM. Three new isoforms of Caenorhabditis elegans UNC-89 containing MLCK-like protein kinase domains. J Mol Biol. 2004 Sep 3;342(1):91-108. PMID:15313609 doi:http://dx.doi.org/10.1016/j.jmb.2004.07.006
- ↑ Blomberg N, Baraldi E, Sattler M, Saraste M, Nilges M. Structure of a PH domain from the C. elegans muscle protein UNC-89 suggests a novel function. Structure. 2000 Oct 15;8(10):1079-87. PMID:11080629
