Interacting selectively and non-covalently with any protein or protein complex (a complex of two or more proteins that may include other nonprotein molecules).
Evidence
1:
Inferred from Physical InteractionIntAct
Characterization of the extracellular protein interactome has lagged far behind that of intracellular proteins, where mass spectrometry and yeast two-hybrid technologies have excelled. Improved methods for identifying receptor-ligand and extracellular matrix protein interactions will greatly accelerate biological discovery in cell signaling and cellular communication. These technologies must be able to identify low-affinity binding events that are often observed between membrane-bound coreceptor molecules during cell-cell or cell-extracellular matrix contact. Here we demonstrate that functional protein microarrays are particularly well-suited for high-throughput screening of extracellular protein interactions. To evaluate the performance of the platform, we screened a set of 89 immunoglobulin (Ig)-type receptors against a highly diverse extracellular protein microarray with 686 genes represented. To enhance detection of low-affinity interactions, we developed a rapid method to assemble bait Fc fusion proteins into multivalent complexes using protein A microbeads. Based on these screens, we developed a statistical methodology for hit calling and identification of nonspecific interactions on protein microarrays. We found that the Ig receptor interactions identified using our methodology are highly specific and display minimal off-target binding, resulting in a 70% true-positive to false-positive hit ratio. We anticipate that these methods will be useful for a wide variety of functional protein microarray users.
We have isolated cDNAs for carcinoembryonic antigen (CEA) and for a normal cross-reacting antigen (NCA) and report here their nucleotide and derived amino acid sequences. Our data show that both the CEA and NCA polypeptides are organized into extracellular domains, some with cysteine-linked loops, that share extensive sequence homology (approximately 78% overall) with each other and appear similar to immunoglobulin superfamily members. A major difference between the two apoproteins is the presence of a single loop-domain in NCA compared to three tandemly repeated loop-domains in CEA. Sequence comparisons between the extracellular domains of CEA and NCA show that the N-terminal and adjacent loop domains of each apoprotein have high homology (85-90%) to each other, while comparison of loop-domain regions reveals a possible nonrandom distribution of base changes and altered amino acids near certain cysteine residues that are inferred to be involved in forming disulfide loops. Both apoproteins show high identity in their hydrophobic C-termini that are reminiscent of the type of transmembrane tails seen in proteins that potentiate signal transduction. These findings, coupled with distinct expression profiles of CEA and NCA mRNAs, suggest that these apoproteins may function as unique cell-surface molecules mediating cell-specific interactions in normal and neoplastic cells.
The cellular process in which a signal is conveyed to trigger a change in the activity or state of a cell. Signal transduction begins with reception of a signal (e.g. a ligand binding to a receptor or receptor activation by a stimulus such as light), or for signal transduction in the absence of ligand, signal-withdrawal or the activity of a constitutively active receptor. Signal transduction ends with regulation of a downstream cellular process, e.g. regulation of transcription or regulation of a metabolic process. Signal transduction covers signaling from receptors located on the surface of the cell and signaling via molecules located within the cell. For signaling between cells, signal transduction is restricted to events at and within the receiving cell.
We have isolated cDNAs for carcinoembryonic antigen (CEA) and for a normal cross-reacting antigen (NCA) and report here their nucleotide and derived amino acid sequences. Our data show that both the CEA and NCA polypeptides are organized into extracellular domains, some with cysteine-linked loops, that share extensive sequence homology (approximately 78% overall) with each other and appear similar to immunoglobulin superfamily members. A major difference between the two apoproteins is the presence of a single loop-domain in NCA compared to three tandemly repeated loop-domains in CEA. Sequence comparisons between the extracellular domains of CEA and NCA show that the N-terminal and adjacent loop domains of each apoprotein have high homology (85-90%) to each other, while comparison of loop-domain regions reveals a possible nonrandom distribution of base changes and altered amino acids near certain cysteine residues that are inferred to be involved in forming disulfide loops. Both apoproteins show high identity in their hydrophobic C-termini that are reminiscent of the type of transmembrane tails seen in proteins that potentiate signal transduction. These findings, coupled with distinct expression profiles of CEA and NCA mRNAs, suggest that these apoproteins may function as unique cell-surface molecules mediating cell-specific interactions in normal and neoplastic cells.
A reference proteome is a set of protein sequences derived from a complete proteome which constitutes a defined standard for a particular user community. Reference proteomes are manually defined according to a number of criteria. They cover the proteomes of well- studied model organisms and other proteomes of interest for biomedical and biotechnological research. Reference proteomes have been selected to provide broad coverage of the tree of life, and constitute a representative cross-section of the taxonomic diversity to be found within UniProtKB.
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