Related Experiment Video
Updated: Aug 10, 2026
Myosin-Specific Adaptations of In vitro Fluorescence Microscopy-Based Motility Assays
Published on: February 4, 2021
Further characterization of proteins associated with elastic fiber microfibrils including the molecular cloning of
M A Gibson1, G Hatzinikolas, J S Kumaratilake
1Department of Pathology, University of Adelaide, Australia.
Abstract:
Together with the 31-kDa microfibril-associated glycoprotein (MAGP), four polypeptides designated MP340 (340 kDa), MP78 (78 kDa), MP70 (70 kDa), and MP25 (25 kDa) have previously been identified in tissue extracts designed specifically to solubilize the microfibrillar component of elastic fibers. In the present study, both MP78 and MP70 were shown to be forms of a protein which is closely related to the human protein beta ig-h3, and MP340 was confirmed to be the bovine form of fibrillin-1. Peptide sequences from MP25 proved to be unique, and affinity-purified anti-MP25 antibodies were shown, by immunofluorescence and immunoelectron microscopy, to localize specifically to the elastin-associated microfibrils. This confirmed that MP25 was a distinct component of these structures. Expression screening of nuchal ligament cDNA libraries yielded a cDNA, cM10A (770 base pairs) which encodes amino acid sequences matching those of the MP25 peptides. Further library screening with cM10A identified cDNAs which encode the complete primary structures of bovine and human MP25. Bovine and human MP25 were found to be around 80% homologous and contain 170 and 173 amino acids, respectively. Data base searches revealed that MP25 had significant similarity of structure only with MAGP, indicating that the two proteins form a new family of microfibrillar proteins. In acknowledgment, MP25 has been formally renamed MAGP-2, and MAGP is referred to as MAGP-1. The close similarity between the two proteins (57%) is confined to a central region of 60 amino acids where there is precise alignment of 7 cysteine residues. Elsewhere the MAGP-2 molecule is rich in serine and threonine residues and contains an RGD motif. MAGP-2 lacks the proline-, glutamine-, and tyrosine-rich sequences and a hydrophobic carboxyl terminus, characteristic of MAGP-1. These structural differences suggest that MAGP-2 has some functions which are distinct from those of MAGP-1. The locus of the human MAGP-2 gene was identified on chromosome 12 in the region of 12p12.3-12p13.1.
Insights
Researchers identified a new microfibrillar protein, MP25, now named microfibril-associated glycoprotein-2 (MAGP-2). This protein, distinct from MAGP-1, forms a new protein family involved in elastic fiber structure.
Area of Science:
- Biochemistry
- Molecular Biology
- Genetics
Background:
- Elastic fibers contain microfibrils composed of various glycoproteins.
- Previous studies identified four polypeptides (MP340, MP78, MP70, MP25) in these microfibrils.
- MP340 is fibrillin-1, MP78/MP70 relate to beta ig-h3, but MP25's identity and function were unclear.
Purpose of the Study:
- To identify and characterize the novel MP25 component of elastic fiber microfibrils.
- To determine the primary structure and evolutionary relationship of MP25.
- To investigate the relationship between MP25 and MAGP-1.
Main Methods:
- Peptide sequencing and antibody generation for MP25.
- Immunofluorescence and immunoelectron microscopy to localize MP25.
- cDNA library screening to obtain full-length MP25 sequences.
- Bioinformatic analysis for structural and sequence homology.
Main Results:
- MP25 was confirmed as a distinct component of elastin-associated microfibrils.
- The complete primary structures of bovine and human MP25 were determined.
- MP25 shares significant structural similarity with MAGP-1, forming a new protein family (MAGP-1 and MAGP-2).
- MP25 was renamed MAGP-2, and MAGP was renamed MAGP-1.
Conclusions:
- MP25 (MAGP-2) and MAGP-1 constitute a new family of microfibrillar proteins.
- Distinct structural features suggest unique functions for MAGP-2.
- The human MAGP-2 gene is located on chromosome 12 (12p12.3-12p13.1).
More Related Videos
06:39Biological Preparation and Mechanical Technique for Determining Viscoelastic Properties of Zonular Fibers
Published on: December 16, 2021
08:12Intact Short, Intermediate, and Long Skeletal Muscle Fibers Obtained by Enzymatic Dissociation of Six Hindlimb Muscles of Mice: Beyond Flexor Digitorum Brevis
Published on: December 1, 2023
Related Concept Videos
02:21Globular and Fibrous Proteins
Globular proteins are also known as spheroproteins and typically are approximately round in shape. They contain a mix of amino acid types and contain differing sequences in their primary structures. Globular proteins have many different functions, such as enzymes, cellular messengers, and molecular transporters. These roles often require the proteins to be...
01:56Structural Protein Function
Collagen, the most abundant protein in mammals, is found throughout the body. In connective tissue, such as skin, ligaments, and tendons, it provides tensile strength and elasticity. In bones and teeth, it mineralizes to form...
01:13Cytoskeletal Accessory Proteins
01:14Generation of Straight or Branched Actin Filaments
Arp2/3 Complex
Arp2/3 complex is a seven-subunit complex consisting of two proteins similar to actin- Arp2 and Arp3, and five other subunits that help keep Arp2 and Arp3 inactive. When required, the complex is...
01:19Actin Filament Depolymerization
In F-actin, the ADF/cofilin proteins...
01:12Elastin is Responsible for Tissue Elasticity
Ligaments and tendons are made of dense regular connective tissue, but in ligaments not all fibers are parallel. Dense regular elastic tissue contains elastin fibers and...