α-La f((61-68)S-S(75-80)) [id=ALA0006]

Synonym: LDC

Producer Organism : Native Protein : Production Method :
Cow α-lactalbumin Enzymatic hydrolysis and Purification with LC method
Activity : Antibacterial
Target Organisms :

Gram-positive: Active against Bacillus subtilis BGA, Micrococcus luteus ATCC 4698, Staphylococcus epidermidis ATCC 12228, Staphylococcus lentus, Streptococcus zooepidemicus, Staphylococcus aureus ATCC 25923C.

Gram-negative: Active against Klebsiella pneumoniae ATCC 13883.

NOTE: No activity against Escherichia coli ATCC 25922, Bordetella bronchiseptica, Serratia marcescens ATCC 8100, Pseudomonas aeruginosa ATCC 27853, Candida albicans ATCC 2091 .

Description :
Production method: Chymotrypsin hydrolysis and purification with LC method.

Length : 15 Mass (Da): 1 650.15 Common Amino Acids : D
Isolectric Point : 5.48 Net Charge : Absent Amino Acids : AEGLMRTVWY
Basic Residues : 3 Acidic Residues : 3 Hydrophobic Residues : 2
Polar Residues : 4 Boman Index : -47.04 Hydropathy Index : -1.24
Aliphatic Index : 26 Instability Index : 0 Extinction Coefficient : 125
Absorbance 280nm : 8.93

Wheel representation

Hydrophobicity plot

Red solid plot : values according to the hydrophobicity scale of Kyte and Doolittle (reference paper).
Yellow dashed plot : Experimentally determined hydrophobicity scale for proteins at membrane interfaces(reference paper).
Green dotted-dashed plot : prediction of transmembrane helices (reference paper). In this scale (unlike the others), more negative values reflect greater hydrophobicity.

Citation: 1

Isolation and identification of three bactericidal domains in the bovine alpha-lactalbumin molecule

Cited Entries: ALA0003, ALA0004, ALA0005, ALA0006

Authors:Pellegrini, A., Thomas, U., Bramaz, N., Hunziker, P., von Fellenberg, R.
Journal: Biochimica et Biophysica Acta (BBA) - General Subjects 1999, 1426(3).
CrossRef External Link
Abstract: Proteolytic digestion of alpha-lactalbumin by pepsin, trypsin and chymotrypsin yielded three polypeptide fragments with bactericidal properties. Two fragments were obtained from the tryptic digestion. One was a pentapeptide with the sequence EQLTK (residues 1-5) and the other, GYGGVSLPEWVCTTF ALCSEK (residues (17-31)S-S(109-114)), was composed of two polypeptide chains held together by a disulfide bridge. Fragmentation of alpha-lactalbumin by chymotrypsin yielded CKDDQNPH ISCDKF (residues (61-68)S-S(75-80)), also a polypeptide composed of two polypeptide chains held together by a disulfide bridge. The three polypeptides were synthesized and found to exert antimicrobial activities. The polypeptides were mostly active against Gram-positive bacteria. Gram-negative bacteria were only poorly susceptible to the bactericidal action of the polypeptides. GYGGVSLPEWVCTTF ALCSEK was most, EQLTK least bactericidal. Replacement of leucine (23) with isoleucine, having a similar chemical structure but higher hydrophobicity, in the sequence GYGGVSLPEWVCTTF ALCSEK significantly reduced the bactericidal capacity of the polypeptide. Digestion of alpha-lactalbumin by pepsin yielded several polypeptide fragments without antibacterial activity. alpha-Lactalbumin in contrast to its polypeptide fragments was not bactericidal against all the bacterial strains tested. Our results suggest a possible antimicrobial function of alpha-lactalbumin after its partial digestion by endopeptidases.
Keywords: [alpha]-Lactalbumin; Antibacterial activity; Antibiotic; Bactericidal peptide

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