Please note: this site relies heavily on the use of javascript. Without a javascript-enabled browser, this site will not function correctly. Please enable javascript and reload the page, or switch to a different browser.
8  structures 514  species 0  interactions 2117  sequences 21  architectures

Family: CDI (PF02234)

Summary: Cyclin-dependent kinase inhibitor

Pfam includes annotations and additional family information from a range of different sources. These sources can be accessed via the tabs below.

This is the Wikipedia entry entitled "Cyclin-dependent kinase inhibitor protein". More...

Cyclin-dependent kinase inhibitor protein Edit Wikipedia article

Cyclin-dependent kinase inhibitor
PDB 1jsu EBI.jpg
Structure of the p27Kip1 cyclin-dependent-kinase inhibitor bound to the cyclin A-Cdk2 complex.[1]

A cyclin-dependent kinase inhibitor protein is a protein which inhibits the enzyme cyclin-dependent kinase (CDK). Several function as tumor suppressor proteins. Cell cycle progression is delayed or stopped by cyclin-dependent kinase inhibitors, abbreviated CDIs, CKIs or CDKIs. CDIs are involved in cell cycle arrest at the G1 phase.

Seven cyclin-dependent kinase inhibitor proteins have thus far been identified. They are named by the small letter "p" followed by their molecular weight in kilodaltons. They are p15, p16, p18, p19, p21, p27, and p57.

Associated gene and target

Protein Gene Target
p16 CDKN2A Cyclin-dependent kinase 4, Cyclin-dependent kinase 6
p15 CDKN2B Cyclin-dependent kinase 4
p18 CDKN2C Cyclin-dependent kinase 4, Cyclin-dependent kinase 6
p19 CDKN2D Cyclin-dependent kinase 4, Cyclin-dependent kinase 6
p21 / WAF1 CDKN1A[2] Cyclin E1/Cyclin-dependent kinase 2
p27 CDKN1B Cyclin D3/Cyclin-dependent kinase 4, Cyclin E1/Cyclin-dependent kinase 2
p57 CDKN1C Cyclin E1/Cyclin-dependent kinase 2
CDKN3 Cyclin-dependent kinase 2


  1. ^ Russo AA, Jeffrey PD, Patten AK, Massagué J, Pavletich NP (July 1996). "Crystal structure of the p27Kip1 cyclin-dependent-kinase inhibitor bound to the cyclin A-Cdk2 complex". Nature. 382 (6589): 325–31. doi:10.1038/382325a0. PMID 8684460.
  2. ^ Hoshino R, Chatani Y, Yamori T, Tsuruo T, Oka H, Yoshida O, Shimada Y, Ari-i S, Wada H, Fujimoto J, Kohno M (January 1999). "Constitutive activation of the 41-/43-kDa mitogen-activated protein kinase signaling pathway in human tumors". Oncogene. 18 (3): 813–22. doi:10.1038/sj.onc.1202367. PMID 9989833.

External links

This page is based on a Wikipedia article. The text is available under the Creative Commons Attribution/Share-Alike License.

This tab holds the annotation information that is stored in the Pfam database. As we move to using Wikipedia as our main source of annotation, the contents of this tab will be gradually replaced by the Wikipedia tab.

Cyclin-dependent kinase inhibitor Provide feedback

Cell cycle progression is negatively controlled by cyclin-dependent kinases inhibitors (CDIs). CDIs are involved in cell cycle arrest at the G1 phase.

Literature references

  1. Lee MH, Reynisdottir I, Massague J; , Genes Dev 1995;9:639-649.: Cloning of p57KIP2, a cyclin-dependent kinase inhibitor with unique domain structure and tissue distribution. PUBMED:7729683 EPMC:7729683

External database links

This tab holds annotation information from the InterPro database.

InterPro entry IPR003175

Cell cycle progression is negatively controlled by cyclin-dependent kinases inhibitors (CDIs). CDIs are involved in cell cycle arrest at the G1 phase. This entry represents a domain found in CDIs [ PUBMED:7729683 ].

Gene Ontology

The mapping between Pfam and Gene Ontology is provided by InterPro. If you use this data please cite InterPro.

Domain organisation

Below is a listing of the unique domain organisations or architectures in which this domain is found. More...

Loading domain graphics...


We store a range of different sequence alignments for families. As well as the seed alignment from which the family is built, we provide the full alignment, generated by searching the sequence database (reference proteomes) using the family HMM. We also generate alignments using four representative proteomes (RP) sets and the UniProtKB sequence database. More...

View options

We make a range of alignments for each Pfam-A family. You can see a description of each above. You can view these alignments in various ways but please note that some types of alignment are never generated while others may not be available for all families, most commonly because the alignments are too large to handle.

Representative proteomes UniProt
Jalview View  View  View  View  View  View  View 
HTML View  View           
PP/heatmap 1 View           

1Cannot generate PP/Heatmap alignments for seeds; no PP data available

Key: ✓ available, x not generated, not available.

Format an alignment

Representative proteomes UniProt

Download options

We make all of our alignments available in Stockholm format. You can download them here as raw, plain text files or as gzip-compressed files.

Representative proteomes UniProt
Raw Stockholm Download   Download   Download   Download   Download   Download   Download  
Gzipped Download   Download   Download   Download   Download   Download   Download  

You can also download a FASTA format file containing the full-length sequences for all sequences in the full alignment.

HMM logo

HMM logos is one way of visualising profile HMMs. Logos provide a quick overview of the properties of an HMM in a graphical form. You can see a more detailed description of HMM logos and find out how you can interpret them here. More...


This page displays the phylogenetic tree for this family's seed alignment. We use FastTree to calculate neighbour join trees with a local bootstrap based on 100 resamples (shown next to the tree nodes). FastTree calculates approximately-maximum-likelihood phylogenetic trees from our seed alignment.

Note: You can also download the data file for the tree.

Curation and family details

This section shows the detailed information about the Pfam family. You can see the definitions of many of the terms in this section in the glossary and a fuller explanation of the scoring system that we use in the scores section of the help pages.

Curation View help on the curation process

Seed source: Pfam-B_1698 (release 5.2) & Pfam-B_5787 (Release 8.0)
Previous IDs: none
Type: Family
Sequence Ontology: SO:0100021
Author: Bateman A , Mian N
Number in seed: 102
Number in full: 2117
Average length of the domain: 48.50 aa
Average identity of full alignment: 34 %
Average coverage of the sequence by the domain: 23.79 %

HMM information View help on HMM parameters

HMM build commands:
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 57096847 -E 1000 --cpu 4 HMM pfamseq
Model details:
Parameter Sequence Domain
Gathering cut-off 20.7 20.7
Trusted cut-off 20.7 20.7
Noise cut-off 20.5 20.6
Model length: 49
Family (HMM) version: 21
Download: download the raw HMM for this family

Species distribution

Sunburst controls


Weight segments by...

Change the size of the sunburst


Colour assignments

Archea Archea Eukaryota Eukaryota
Bacteria Bacteria Other sequences Other sequences
Viruses Viruses Unclassified Unclassified
Viroids Viroids Unclassified sequence Unclassified sequence


Align selected sequences to HMM

Generate a FASTA-format file

Clear selection

This visualisation provides a simple graphical representation of the distribution of this family across species. You can find the original interactive tree in the adjacent tab. More...

Loading sunburst data...

Tree controls


The tree shows the occurrence of this domain across different species. More...


Please note: for large trees this can take some time. While the tree is loading, you can safely switch away from this tab but if you browse away from the family page entirely, the tree will not be loaded.


For those sequences which have a structure in the Protein DataBank, we use the mapping between UniProt, PDB and Pfam coordinate systems from the PDBe group, to allow us to map Pfam domains onto UniProt sequences and three-dimensional protein structures. The table below shows the structures on which the CDI domain has been found. There are 8 instances of this domain found in the PDB. Note that there may be multiple copies of the domain in a single PDB structure, since many structures contain multiple copies of the same protein sequence.

Loading structure mapping...