Isolation and sequence analysis of amyloid protein AA from a patient with cystic fibrosis
M Skinner1, A Pinnette, W D Travis
1Arthritis Center, Boston University School of Medicine, MA 02118.
Abstract:
This study represents the first sequence analysis of an amyloid fibril protein from a patient with cystic fibrosis. Although chronic infections are a hallmark of cystic fibrosis, secondary amyloidosis is a rare complication, and during the past 20 years, only 16 cases of amyloidosis in patients with cystic fibrosis have been reported. We examined amyloid fibrils isolated from the spleen of a 25-year-old man who had a history of a chronic cough since infancy and a diagnosis of cystic fibrosis at age 6 years. After solubilization in 6 mol/L guanidine and purification by gel filtration, the major component of the amyloid fibrils was a homogeneous 8000 dalton protein that reacted positively with antiserum to human amyloid A (AA) protein. Complete protein sequence analysis was carried out by using the whole protein and fragments obtained by treatment of the protein with cyanogen bromide, lysyl endopeptidase, and carboxypeptidase. The protein contained 76 residues and showed minor heterogeneity when compared with other AA protein sequences. The cystic fibrosis AA protein represents a product of the SAA-specific cDNA clone now known to be the alpha-allelic form of SAA1 in which valine is present at position 52 and alanine is at position 57.
Insights
This study sequenced amyloid protein in cystic fibrosis, revealing it as a rare complication. The identified protein, amyloid A (AA), showed minor sequence differences compared to typical AA proteins.
Area of Science:
- Biochemistry
- Medical Genetics
- Pathology
Background:
- Cystic Fibrosis (CF) is characterized by chronic infections, but secondary amyloidosis is a rare complication.
- Only 16 cases of amyloidosis in CF patients have been reported in the last 20 years.
- Amyloidosis involves the abnormal deposition of proteins, leading to organ damage.
Purpose of the Study:
- To perform the first sequence analysis of an amyloid fibril protein from a cystic fibrosis patient.
- To characterize the specific amyloid protein involved in secondary amyloidosis in CF.
- To compare the identified protein sequence with known amyloid A (AA) protein sequences.
Main Methods:
- Amyloid fibrils were isolated from the spleen of a CF patient.
- The major protein component was solubilized and purified using gel filtration.
- Complete protein sequence analysis was performed using enzymatic and chemical fragmentation methods.
Main Results:
- The major component of the amyloid fibrils was identified as human amyloid A (AA) protein.
- The protein consisted of 76 residues and exhibited minor sequence heterogeneity compared to other AA proteins.
- The identified AA protein corresponds to the alpha-allelic form of SAA1, with specific amino acid variations at positions 52 and 57.
Conclusions:
- This study provides the first detailed sequence analysis of AA protein in cystic fibrosis-associated secondary amyloidosis.
- The findings contribute to understanding the molecular basis of this rare complication in CF.
- The identified protein sequence variations may offer insights into the pathogenesis of amyloidosis in CF patients.
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