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Science. 2005 May 13;308(5724):1032-4. Epub 2005 Mar 31.

Human Mpp11 J protein: ribosome-tethered molecular chaperones are ubiquitous.

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Department of Biochemistry, 433 Babcock Drive, University of Wisconsin-Madison, Madison, WI 53706, USA.


The existence of specialized molecular chaperones that interact directly with ribosomes is well established in microorganisms. Such proteins bind polypeptides exiting the ribosomal tunnel and provide a physical link between translation and protein folding. We report that ribosome-associated molecular chaperones have been maintained throughout eukaryotic evolution, as illustrated by Mpp11, the human ortholog of the yeast ribosome-associated J protein Zuo. When expressed in yeast, Mpp11 partially substituted for Zuo by partnering with the multipurpose Hsp70 Ssa, the homolog of mammalian Hsc70. We propose that in metazoans, ribosome-associated Mpp11 recruits the multifunctional soluble Hsc70 to nascent polypeptide chains as they exit the ribosome.

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