Probable role of amphiphilicity in the binding of mastoparan to calmodulin

McDowell, Lynda M.; Sanyal, Gautam; Prendergast, Franklyn G.

doi:10.1021/bi00333a026

Cited by 83 publications

(81 citation statements)

References 20 publications

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“…3 and are shown in Table 2. As can be seen from the table, the mean fluorescence lifetime of monomeric melittin in aqueous solution is 3.5 ns, in agreement with previous literature (McDowell et al 1985;Pandit et al 2003). The mean fluorescence lifetimes of melittin in micelles of various surface charges are different, indicating that the local environment experienced by the tryptophan residue is different in these cases.…”

Section: Fluorescence Polarization Of Micelle-bound Melittinsupporting

confidence: 91%

Effect of micellar charge on the conformation and dynamics of melittin

Raghuraman

Chattopadhyay

2004

Eur Biophys J

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Electrostatic interactions play a crucial role in modulating and stabilizing molecular interactions in membranes and membrane-mimetic systems such as micelles. We have monitored the change in the conformation and dynamics of the cationic hemolytic peptide melittin bound to micelles of various charge types, utilizing fluorescence and circular dichroism (CD) spectroscopy. The sole tryptophan of melittin displays a red-edge excitation shift (REES) of 3-6 nm when bound to anionic, nonionic, and zwitterionic micelles. This suggests that melittin is localized in a restricted environment, probably in the interfacial region of the micelles, and this region offers considerable restriction to the reorientational motion of the solvent dipoles around the excited state tryptophan in melittin. Further, the rotational mobility of melittin is considerably reduced in these micelles and is found to be dependent on the surface charge of micelles. Interestingly, our results show that melittin does not partition into cetyltrimethylammonium bromide (CTAB) micelles owing to electrostatic repulsion between melittin and CTAB micelles, both of which carry a positive charge. In addition, the fluorescence lifetime of melittin is modulated in micelles of different charge types. The lowest mean fluorescence lifetime is observed in the case of melittin bound to anionic sodium dodecyl sulfate (SDS) micelles. CD spectroscopy shows that micelles induce significant helicity to melittin, with maximum helicity being induced in the case of melittin bound to SDS micelles. Fluorescence quenching measurements using the neutral aqueous quencher acrylamide show differential accessibility of melittin in various types of micelles. Taken together, our results show that micellar surface charge can modulate the conformation and dynamics of melittin. These results could be relevant to understanding the role of the surface charge of membranes in the interaction of membrane-active, amphiphilic peptides with membranes.

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Section: Fluorescence Polarization Of Micelle-bound Melittinsupporting

confidence: 91%

Effect of micellar charge on the conformation and dynamics of melittin

Raghuraman

Chattopadhyay

2004

Eur Biophys J

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“…A likely candidate is the central portion of the helix 66-92 which is not well defined in the crystal structure. However, it would need to be discontinuous in this enhanced helical solution conformation, in order to maintain a more compact hydrodynamic volume [27] Likewise, in other model systems, CD [38] and NMR [39] studies show that the peptide mellitin adopts a helical conformation on binding to Gas-calmodulin, as does mastoparan [40]. Although helix formation is not an essential prerequisite for binding to Ca4-calmodulin (or troponin C, as suggested by the troponin-I inhibitory peptide (104-115) [41]) it appears quite common.…”

Section: Discussionmentioning

confidence: 99%

The conformation of calmodulin: A substantial environmentally sensitive helical transition in Ca₄‐calmodulin with potential mechanistic function

1988

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The conformation of Ca,-calmodulin in solution, as assessed by far-UV peptide circular dichroism, contains significantly less a-helix than the proposed X-ray crystal structure. We now show that Ca,-calmodulin adopts significant additional helical structure in solution in the presence of a hehcogenic solvent (50%;, v/v, aqueous 2,2,2+ifluoroethanol or 50& v/v, methylpentane-5,Sdiol).We suggest that the long continuous helix (residues 6692 of the crystal structure) is not necessarily a normal feature of the calmodulin structure in solution, and may be due in part to the conditions of crystallisation. This result is supported by time-resolved tyrosine fluorescence anisotropy studies indicating that Ca,-calmodulin in solution is an essentially compact globular structure which undergoes isotropic rotational motion. We conclude that, under appropriate ionic and apolar environmental conditions, Ca,-calmodulin undergoes a substantial helical transition, which may involve residues in the central region of the molecule. Such a transition could have an important function in determining specificity and affinity in interactions of calmodulin with different target sequences of Ca*+-dependent regulatory enzymes.

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“…The most unusual feature of the calmodulinbinding domain identified in Ral-A is that it is rather more hydrophilic than hydrophobic, because it contains 9 of 18 hydrophilic amino acids (50%) but only four hydrophobic residues (22%). By contrast, the mastoparans, high affinity calmodulinbinding peptides, have 21-28% hydrophilic amino acids and 36 -50% hydrophobic residues (46). Although it has been established that the interaction of calmodulin with its target proteins is predominantly hydrophobic, it is complemented by acidic side chains from the calmodulin EF-hands interacting with basic residues of the target proteins (47).…”

Section: Figmentioning

confidence: 99%