Fesselin is a natively unfolded protein.
Fesselin is a heat stable proline-rich actin binding protein. The stability, amino acid composition, and ability to bind to several proteins suggested that fesselin may be unfolded under native conditions. While the complete sequence of fesselin is unknown an analysis of a closely related protein, synaptopodin 2 from Gallus gallus, indicates that fesselin consists of a series of unstructured regions interspersed between short folded regions. To determine if fesselin is natively unfolded, we compared fesselin to a known globular protein (myosin S1) and a known unfolded protein Cad22 (the COOH terminal 22 kDa fragment of caldesmon). Fesselin, and Cad22, had larger Stokes radii than globular proteins of equivalent mass. The environments of tryptophan residues of fesselin and Cad22 were the same in the presence and absence of 6 M guanidine hydrochloride. Fesselin had a circular dichroism spectrum that was primarily random coil. Changes in pH over the range of 1.5-11.5 did not alter that spectrum. Increasing the temperature to 85 degrees C caused an increase in the degree of secondary structure. Calmodulin binding to fesselin altered the environment of the tryptophan residues so that they became less sensitive to the quencher acrylamide. These results show that fesselin is a natively unfolded protein.
Khaymina
Svetlana S
SS
Departments of Biochemistry and Molecular Biology and Physics, Brody School of Medicine at East Carolina University, 600 Moye Boulevard, Greenville, North Carolina 27834, USA.
Kenney
John M
JM
Schroeter
Mechthild M
MM
Chalovich
Joseph M
JM
D000596:Amino Acids / Q000737:chemistry; D000818:Animals; D002645:Chickens; D004777:Environment; D019791:Guanidine / Q000737:chemistry; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D008565:Membrane Proteins / Q000737:chemistry*; D008840:Microfilament Proteins / Q000737:chemistry*; D015879:Myosin Subfragments / Q000737:chemistry; D011392:Proline / Q000737:chemistry; D011485:Protein Binding; D011489:Protein Denaturation; D017510:Protein Folding; D013050:Spectrometry, Fluorescence; D014364:Tryptophan / Q000737:chemistry
D000596:Amino Acids; D008565:Membrane Proteins; D008840:Microfilament Proteins; D015879:Myosin Subfragments; C443099:fesselin; D014364:Tryptophan; D011392:Proline; D019791:Guanidine