Structural Relationship Between Human Salivary Histatins

Abstract

Histatins are a group of electrophoretically distinct histidine-rich polypeptides with microbicidal activity found in human parotid and submandibular gland secretions. Recently, we have shown that histatins 1, 3, and 5 are homologous proteins that consist of 38, 32, and 24 amino acid residues, respectively, and that these polypeptides kill the pathogenic yeast, Candida albicans. We now describe the isolation and structural characterization of histatins 2, 4, 6, and 7-12, the remaining members ofthis group ofpolypeptides. Histatin 2 wasfound to be identical to the carboxyl terminal 26 residues of histatin 1; histatin 4 was found to be identical to the carboxyl terminal 20 residues of histatin 3; and histatin 6 was found to be identical to histatin 5, but contained an additional carboxyl terminal arginine residue. The amino acid sequences of histatins 7-12 formally correspond to residues 12-24, 13-24, 12-25, 13-25, 5-11, and 5-12, respectively, of histatin 3, but could also arise proteolytically from histatin 5 or 6. These results establish, for the first time, the complete structural relationships between all members of this group ofmicrobicidal proteins in human parotid saliva. The relationship of histatins to one another is discussed in the context of their genetic origin, biosynthesis and secretion into the oral cavity, and potential as reagents in anti-candidal studies.

Characterization of Histatin 5 with Respect to Amphipathicity, Hydrophobicity, and Effects on Cell and Mitochondrial Membrane Integrity Excludes a Candidacidal Mechanism of Pore Formation

“…From this suspension, 250 l was added to 250 l of a dilution of histatin 5, dhvar1, or dhvar4 in the same buffer. After 0, 6,12,18,24,30,40,60, and 90 min of incubation in a 37°C water bath, 50-l samples were diluted in 9 ml of phosphate-buffered saline and mixed. From this suspension, 25 l was plated on Sabouraud dextrose agar and incubated for 48 h at 30°C to determine the percentage reduction in viable counts.…”

“…Histatins are a group of histidinerich cationic peptides that are secreted by the parotid and the submandibular/sublingual human salivary glands (10,11). At least 12 fragments have been identified (12) that derive from the proteolytic degradation of two gene products, histatin 1 and histatin 3 (13). Histatin 5 has been shown to be the most potent member with respect to its fungicidal activity against the oral opportunistic pathogen Candida albicans, and the domain responsible for this activity has been located in the C-terminal 14 residues (14,15).…”

The human salivary peptide histatin 5 exerts its antifungal activity through the formation of reactive oxygen species

“…istatins constitute a distinct family of at least 12 low molecular weight, histidine-rich, cationic, salivary peptides, of which histatin 1, 3, and 5, containing 38, 32, and 24 amino acids, are the most abundant (1,2). Major interest in histatins stems from the fact that they exhibit cidal activities against a broad range of pathogenic fungi, including Candida albicans, Cryptococcus neoformans, and Aspergillus fumigatus (1,(3)(4)(5).…”

Respiratory inhibition of isolated mammalian mitochondria by salivary antifungal peptide histatin-5

“…The primary structure of the major family members (Hist-1, -3, and -5) has been determined and indicates that these peptides consist of 38, 32, and 24 amino acids, respectively [3,4]. Many of the smaller members of the histatin family are proteolytic products of Hist-1 and Hist-3.…”