Hostname: page-component-848d4c4894-2pzkn Total loading time: 0 Render date: 2024-05-20T03:23:26.785Z Has data issue: false hasContentIssue false

Sequence analysis of Camelus dromedarius milk caseins

Published online by Cambridge University Press:  01 May 1998

STEFAN KAPPELER
Affiliation:
Laboratorium für Milchwissenschaft, Institut für Lebensmittelwissenschaft, Eidgenössische Technische Hochschule, CH-8092 Zürich, Schweiz
ZAKARIA FARAH
Affiliation:
Laboratorium für Milchwissenschaft, Institut für Lebensmittelwissenschaft, Eidgenössische Technische Hochschule, CH-8092 Zürich, Schweiz
ZDENKO PUHAN
Affiliation:
Laboratorium für Milchwissenschaft, Institut für Lebensmittelwissenschaft, Eidgenössische Technische Hochschule, CH-8092 Zürich, Schweiz

Abstract

αs1-, αs2-, β- and κ-caseins from Somali camels (Camelus dromedarius) were purified by acid precipitation at pH 4·4, crudely separated into an α-CN and a β-CN fraction and further purified by reversed-phase HPLC. Fragments of tryptic digests were sequenced. Amino acid patterns obtained were used to screen a cDNA library constructed from mRNA from lactating udder tissue. Full length clones corresponding to the four caseins were sequenced. The numbers of residues in the sequences deduced were αs1-CN 207, αs2-CN 178, β-CN 217, κ-CN 162. Percentage similarity to bovine proteins was αs1-CN A 39, αs2-CN 56, β-CN 64, κ-CN 56. Acid-precipitated casein of pooled milk was separated by reversed-phase HPLC and monitored at 220 nm, and its composition, estimated from peak integration, was (g/kg total casein) αs1-CN 220, αs2-CN 95, β-CN 650, κ-CN 35. Degrees of phosphorylation and glycosylation were determined by laser ionization mass spectrometry and sequence pattern analysis. Molecular masses determined were (kDa) αs1-CN A, 24·755 and 24·668; αs1-CN B, 25·293; αs2-CN 21·993; β-CN, 24·900; κ-CN 22·294–22·987. The pH values of the most probable isoelectric points were: αs1-CN A 6P 4·41, αs1-CN B 6P 4·40, αs2-CN 9P 4·58, β-CN 4P 4·66, κ-CN 1P, with ten sialic acid residues bound, 4·10.

Type
Research Article
Copyright
Proprietors of Journal of Dairy Research 1998

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)