TY - JOUR
T1 - Candidacidal activity prompted by N-terminus histatin-like domain of human salivary mucin (MUC7)
AU - Gururaja, Tarikere L.
AU - Levine, Joseph H.
AU - Tran, Duy T.
AU - Naganagowda, Gowda A.
AU - Ramalingam, Kalaiyarasi
AU - Ramasubbu, Narayanan
AU - Levine, Michael J.
N1 - Funding Information:
This work was supported by USPHS Research Grants DE07585 and DE08240. We thank Hsiaoyun Tsai and Hong-Seop Kho for their assistance in carrying out the candidacidal assays.
PY - 1999/4/12
Y1 - 1999/4/12
N2 - Histidine-rich peptides (histatins, Hsn) in saliva are thought to provide a non-immune defense against Candida albicans. Sequence homology search of the human salivary mucin, MUC7, against histatins revealed a domain at the N-terminus (R3-Q17) having 53% identity to Hsn-5. To determine its candidacidal activity, this 15 residue basic histidine-rich domain of MUC7 (I) was prepared by solid-phase Fmoc chemistry. Various N- and C-terminal protected derivatives of I were also synthesized to correlate the effect of peptide overall charge in exhibiting cidal potency. Candidacidal activity measurement of I and its variants showed considerable ED50 values (effective dosage required to kill 50% of candida cells), albeit greater than Hsn-5 (ED50 ~4-6 μM). Of the various analogs tested, N-terminal free acid (I, ED50 ~40 μM) and amide (V, ED50~16 μM) exhibited appreciable candidacidal activities suggesting the possible role of peptide net charge in cidal action. Blocking of N-terminus with a bulky octanoyl group showed only marginal effect on the cidal activity of I or V, indicating that hydrophobicity of these synthetic constructs may not be important for exerting such activities. Membrane-induced conformational transition from random coil to helical structures of all the test peptides implied their tendency to adapt order structures at the lipid-membrane interface similar to that of Hsn-5. However, comparison of propensity for helical structure formation vs. ED50 indicated that cidal potency of MUC7 Hsn-like peptides depends largely on electrostatic interactions irrespective of secondary structural elements. Delineation of solution structure of the most active peptide (V) by 2D-NMR revealed essentially a non-structured conformation in aqueous medium, which further supported the fact that the peptide helical structure may not be a prerequisite for posing candidacidal activity. The formation of smaller truncated peptides and/or Hsn-like fragments on proteolytic degradation of intact MUC7 in the presence of oral flora provided indirect evidence that mucin could serve as a backup candidacidal agent to salivary Hsn. Copyright (C) 1999 Elsevier Science B.V.
AB - Histidine-rich peptides (histatins, Hsn) in saliva are thought to provide a non-immune defense against Candida albicans. Sequence homology search of the human salivary mucin, MUC7, against histatins revealed a domain at the N-terminus (R3-Q17) having 53% identity to Hsn-5. To determine its candidacidal activity, this 15 residue basic histidine-rich domain of MUC7 (I) was prepared by solid-phase Fmoc chemistry. Various N- and C-terminal protected derivatives of I were also synthesized to correlate the effect of peptide overall charge in exhibiting cidal potency. Candidacidal activity measurement of I and its variants showed considerable ED50 values (effective dosage required to kill 50% of candida cells), albeit greater than Hsn-5 (ED50 ~4-6 μM). Of the various analogs tested, N-terminal free acid (I, ED50 ~40 μM) and amide (V, ED50~16 μM) exhibited appreciable candidacidal activities suggesting the possible role of peptide net charge in cidal action. Blocking of N-terminus with a bulky octanoyl group showed only marginal effect on the cidal activity of I or V, indicating that hydrophobicity of these synthetic constructs may not be important for exerting such activities. Membrane-induced conformational transition from random coil to helical structures of all the test peptides implied their tendency to adapt order structures at the lipid-membrane interface similar to that of Hsn-5. However, comparison of propensity for helical structure formation vs. ED50 indicated that cidal potency of MUC7 Hsn-like peptides depends largely on electrostatic interactions irrespective of secondary structural elements. Delineation of solution structure of the most active peptide (V) by 2D-NMR revealed essentially a non-structured conformation in aqueous medium, which further supported the fact that the peptide helical structure may not be a prerequisite for posing candidacidal activity. The formation of smaller truncated peptides and/or Hsn-like fragments on proteolytic degradation of intact MUC7 in the presence of oral flora provided indirect evidence that mucin could serve as a backup candidacidal agent to salivary Hsn. Copyright (C) 1999 Elsevier Science B.V.
KW - 2D-NMR
KW - Candida albicans
KW - Candidacidal activity
KW - Circular dichroism
KW - Histatin-like domain
KW - Human salivary mucin
KW - Peptide synthesis
KW - Solution conformation
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U2 - 10.1016/S0167-4838(99)00034-5
DO - 10.1016/S0167-4838(99)00034-5
M3 - Article
C2 - 10209284
AN - SCOPUS:0032934508
SN - 0167-4838
VL - 1431
SP - 107
EP - 119
JO - Biochimica et Biophysica Acta - Protein Structure and Molecular Enzymology
JF - Biochimica et Biophysica Acta - Protein Structure and Molecular Enzymology
IS - 1
ER -