Plg-RKT Membrane Protein Isolation via Biotinylation
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Solution Overview
Problem
Current methods fail to identify integral membrane proteins with carboxyl-terminal lysines as plasminogen receptors, which are crucial for cell surface proteolysis in physiological and pathological processes, due to limitations in resolution techniques like SDS gels.
Innovation Solution
A novel purification procedure involving biotinylation, affinity chromatography, and multidimensional protein identification technology (MudPIT) is used to isolate and characterize a Type II transmembrane protein, C9orf46 homolog, termed Plg-RKT, which exposes a carboxyl-terminal lysine and functions as a plasminogen receptor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If SDS gel electrophoresis is used to isolate and characterize plasminogen binding proteins, then the process is simple and widely applicable, but the resolution of integral membrane proteins is poor
Solution Approach 1:
The patent changes the purification parameters from standard SDS gel electrophoresis to a specialized protocol involving biotinylation, affinity chromatography on plasminogen-Sepharose, and multidimensional protein identification technology (MudPIT). This parameter change enables the resolution and identification of integral membrane proteins that were previously undetectable, while maintaining feasibility through systematic methodology.
Solution Approach 2:
The patent introduces biotin as an intermediary molecule to facilitate protein isolation. By biotinyating integral membrane proteins and using avidin-biotin interaction on plasminogen-Sepharose columns, the method creates a specific binding mechanism that enables selective isolation and identification of plasminogen binding proteins, including integral membrane proteins that evade conventional SDS gel detection.
2Ease of manufacture
If conventional purification methods are used to search for integral membrane proteins with carboxyl terminal lysines, then the process is straightforward, but such proteins remain unidentified
Solution Approach 1:
The patent segments the purification process into distinct functional steps: biotinylation of integral membrane proteins, affinity chromatography on plasminogen-Sepharose to separate plasminogen binding proteins, trypsin digestion for protein identification, and MudPIT for multidimensional analysis. This segmentation enables systematic identification of proteins with carboxyl terminal lysines that bind plasminogen, overcoming the limitations of conventional single-step methods.
Solution Approach 2:
The patent replaces conventional mechanical separation methods (SDS gel electrophoresis) with a biochemical approach using biotin-avidin interaction and affinity chromatography. This substitution enables the detection and identification of integral membrane proteins with carboxyl terminal lysines that are invisible to traditional mechanical separation techniques, thereby preventing loss of critical identification information.
3Quantity of substance
If carboxyl terminal lysines are removed from cell surfaces by carboxypeptidase B, then plasminogen binding capacity is reduced, but the specific plasminogen binding sites are blocked
Solution Approach 1:
The patent applies preliminary anti-action by using carboxypeptidase B treatment as a selective removal method to identify and isolate integral membrane proteins with carboxyl terminal lysines. By pre-treating cells with CpB to remove surface lysines, then applying biotinylation and affinity chromatography, the method selectively targets and identifies the specific plasminogen binding sites that were blocked, thereby maintaining reliability of binding site identification while reducing overall binding capacity for analysis.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The identification of Plg-RKT provides a specific plasminogen-binding protein that modulates cell surface proteolysis, facilitating processes like inflammation, tissue remodeling, and cancer metastasis, and offers a method for detecting inflammation and cancer using anti-Plg-RKT antibodies.
Implementation Method 1
membrane fractions were prepared and isolated by affinity chromatography on plasminogen-Sepharose. The proteins that bound specifically to plasminogen-Sepharose were then captured on avidin-Sepharose
Implementation Method 2
The proteins that bound specifically to plasminogen-Sepharose were then captured on avidin-Sepharose, digested with trypsin and subjected to multidimensional protein identification technology (MudPIT)
Implementation Method 3
Intact cells were biotinylated and then either untreated or treated with CpB (to remove carboxyl terminal lysines). Then membrane fractions were prepared and isolated by affinity chromatography on plasminogen-Sepharose
Data Source
AI summary
The invention relates to C9orf46 homolog, a novel murine membrane protein, and its orthologs in human, mouse and all other species, termed Plg-RKT, or analogs, thereof and the isolation method. The function of this molecule is to bind to plasminogen, plasminogen fragments such as angiostatin1 and other plasminongen fragments having angiostatic activity, tissue plasminogen activator and Lipoprotein(a). Plasminogen receptors function to modulate cell surface proteolysis and physiological and pathophysiological processes requiring cell migration, including, but not limited to, cell migration during inflammation, tissue remodeling, wound healing, tumor cell invasion and metastasis, skeletal myogenesis, neurite outgrowth. Plasminogen receptors also modulate apoptosis and cell death. The invention also relates to antibodies that inhibit plasminogen, plasminogen fragments such as angiostatin1 and other plasminongen fragments having angiostatic activity, tissue plasminogen activator or Lipoprotein(a) binding to Plg-RKT and/or immunoreact with Plg-RKT.